Is it a sin if I don’t go to church? Am I a bad person if I do not attend church regularly?

We have been commanded to attend church and to worship God on the Lord’s day in many places throughout the scriptures. One of the Big Ten is to keep the Sabbath day holy. The author of Hebrews (v. Hebrews 10:23-25) enjoins us as Christians to:

...Hold fast the profession of our faith without wavering; (for he is faithful that promised;) And let us consider one another to provoke unto love and to good works: Not forsaking the assembling of ourselves together, as the manner of some is; but exhorting one another: and so much the more, as ye see the day approaching.

Paul goes on to exhort us to: Let the word of Christ dwell in you richly in all wisdom; teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord. (Colossians 3:16)

A more specific set of instructions is contained in Doctrine and Covenants section 59:7-12 where the Lord commands:

Thou shalt thank the Lord thy God in all things. Thou shalt offer a sacrifice unto the Lord thy God in righteousness, even that of a broken heart and a contrite spirit. And that thou mayest more fully keep thyself unspotted from the world, thou shalt go to the house of prayer and offer up thy sacraments upon my holy day; For verily this is a day appointed unto you to rest from your labors, and to pay thy devotions unto the Most High; Nevertheless thy vows shall be offered up in righteousness on all days and at all times; But remember that on this, the Lord’s day, thou shalt offer thine oblations and thy sacraments unto the Most High, confessing thy sins unto thy brethren, and before the Lord.

Just because we have been commanded to attend church doesn’t mean that you should attend church just because you are afraid that you will be punished for skipping church. Compulsory church attendance defeats the purpose of going to church in the first place. I have found that there is a tendency among members of the LDS church to equate regular attendance with righteousness. This is often accompanied by the implicit conclusion that those who do not attend church regularly must therefore be wicked in some way. While it is assuredly true that those who are truly converted (and who therefore are striving to be as righteous as a flawed mortal can be) tend to attend church as regularly as is within their power (out of a sincere love and devotion to God), it does not necessarily follow that those who attend church regularly are, by default association, righteous by virtue of their regular attendance alone.

"Some have come to think of activity in the Church as the ultimate goal. Therein lies a danger. It is possible to be active in the Church and less active in the gospel. Let me stress: activity in the Church is a highly desirable goal; however, it is insufficient. Activity in the Church is an outward indication of our spiritual desire. If we attend our meetings, hold and fulfill Church responsibilities, and serve others, it is publicly observed. By contrast, the things of the gospel are usually less visible and more difficult to measure, but they are of greater eternal importance. For example, how much faith do we really have? How repentant are we? How meaningful are the ordinances in our lives? How focused are we on our covenants?" (Donald L. Hallstrom, "Converted to His Gospel through His Church", Ensign May 2012)

Attending church is meant to be an expression of one’s gratitude towards and love and devotion for God and his son Jesus Christ (or in short, an outward expression of our inward conversion to the gospel of Christ), and if you are only there out of fear or out of some grudging sense of obligation, then you are missing the point entirely. This is a question of rules-based obedience versus principle-based obedience. It’s not enough to attend out of mindless habit or the desire to be gain the approval of those in your faith community either. In God's eyes, External performance is meaningless without true inner devotion.

Psalms 51:10, 16-17, 6: Create in me a clean heart, O God; and renew a right spirit within me. For thou desirest not sacrifice; else would I give it: thou delightest not in burnt offering. The sacrifices of God are a broken spirit: a broken and a contrite heart, O God, thou wilt not despise. Behold, thou desirest truth in the inward parts: and in the hidden part thou shalt make me to know wisdom.

Moroni 7:6-7: For behold, God hath said a man being evil cannot do that which is good; for if he offereth a gift, or prayeth unto God, except he shall do it with real intent it profiteth him nothing. For behold, it is not counted unto him for righteousness.

Matthew 6:5-6: And when thou prayest, thou shalt not be as the hypocrites are: for they love to pray standing in the synagogues and in the corners of the streets, that they may be seen of men. Verily I say unto you, They have their reward. But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly.

"The Savior often denounced those who did without being—calling them hypocrites: “This people honoureth me with their lips, but their heart is far from me” (Mark 7:6). To do without to be is hypocrisy, or feigning to be what one is not—a pretender.

Conversely, to be without to do is void, as in “faith, if it hath not works, is dead, being alone” (James 2:17; emphasis added). Be without do really isn’t being—it is self-deception, believing oneself to be good merely because one’s intentions are good.

Do without be—hypocrisy—portrays a false image to others, while be without do portrays a false image to oneself." (Lynn G. Robbins, "What Manner of Men and Women Ought Ye to Be?", Ensign May 2011)

James 2:17-18: Even so faith, if it hath not works, is dead, being alone. Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.

In short we need to become both inwardly as well as outwardly converted to the gospel. Once we can achieve that true inward conversion to the gospel then we will naturally do the outward things such as attending church regularly, which are still vital for our spiritual well-being.

"We must diligently search into, and set in order both the outward and the inner man, because both of them are of importance to our progress in godliness." (Thomas of Kempis, The Imitation of Christ, 31)

Elder Hallstrom continues: "I repeat: we need the gospel and the Church. In fact, the purpose of the Church is to help us live the gospel. We often wonder: How can someone be fully active in the Church as a youth and then not be when they are older? How can an adult who has regularly attended and served stop coming? How can a person who was disappointed by a leader or another member allow that to end their Church participation? Perhaps the reason is they were not sufficiently converted to the gospel—the things of eternity." (Donald L. Hallstrom, "Converted to His Gospel through His Church", Ensign May 2012)

That isn't to say that you shouldn't go if you don't feel highly motivated to be at church-quite the opposite in fact! What it does mean is that you should do everything you can to become converted to the principle of attending church for the right reasons. The first step towards that conversion starts with making a fundamental effort to BE at church, and you can worry about the loftier reasons for being there once you're in the door. The fact that we have a church to attend at all is meant to be a blessing to us, to aid us in our lives, and in the long run to help us to return to live with God someday. While going to church is better for you than the alternative, simply being present at church is not enough to receive the great blessings that come through living this principle, as Elder Dallin H. Oaks teaches us:

“[Some people] may attend sporadically, but they are not yet enjoying the full blessings of Church participation and service. Others may attend regularly, but refrain from commitments and from seeking the personal spiritual rebirth that comes from yielding our hearts to God. Both kinds are missing some unique blessings in this life. And both are in jeopardy of missing the most glorious blessings in the life to come.” (Dallin H. Oaks, “The Gospel in Our Lives,” Liahona, Jul 2002, 36–39).

To gain the full benefit of true worship, one must be prepared to make and keep commitments, and to attend with an open heart, ready to be taught by the spirit. Going to church isn’t all about receiving though; a fundamental principle of Christianity is selfless service as an expression of Christ-like love. As Christ is quoted (by Paul) as saying in Acts 20:35, It is more blessed to give than receive. In order to truly experience the full intent behind God’s commandment to attend church, we must come in a spirit of service and giving, without expectation of reward. Where church is concerned, when we stop focusing on “What’s in it for me” at church, only then we will receive the enlightenment we seek.

My answer then, is yes, it does constitute disobedience to God’s commandment to not go to church, but I don't think you are a sinner just because you haven't been to church in a while-or rather, to clarify, I do not think you are any more or less of a sinner than the people who happen to make it into the building each Sunday.  That said, the worrying about whether or not it’s a sin only serves to distract from the things that really matter, which are these:

1) that there are blessings that you can gain at church that you are missing when you are not at church. 

2) You should only feel obligated to go to church for the benefit of two people: you and God, but obligation is a bad reason to do anything.  Frankly, God can get along without you if he has to but you can't get along without him.  Make your decision accordingly.