I greatly appreciate your honesty in your question and I’m glad you do not want to sin.  I want to council you with a couple of Bible verses that readily come to mind. 1 Thessalonians 5:22 tells us to, “Abstain from all appearance of evil.”  As believers on the Lord Jesus Christ, the Lord does not want us to engage in any activity that gives the appearance of sin.  When people realize that you and your boyfriend are living together, what do they think about what you may be doing?  Even though you may not be sleeping together, you are probably giving the appearance that you are.  How does this behavior reflect on the Lord?  Do you think this living arrangement honors the Lord, or does it dishonor Him by giving the impression that you are living in sin?  Many people today will say they do not worry or care about what others think of them.  However, as Christians, we represent the Lord here on the earth and our behavior should reflect His holiness and righteousness. 

Now, let’s read 1 Corinthians 6:18, “Flee fornication.”  You may be determined that if you live in this situation, you will not sin by having sex.  From your question, it seems your boyfriend is not as convinced as you are that you should not sleep together before marriage.  Even with the best of intentions, you may be tempted to answer to the appeal of your fleshly desires.  Since you have repented of having sex before marriage, this shows you have been sexually active with your boyfriend in the past.  With that familiarity, it would be so easy to engage in sex again. Perhaps you might have sex, and then determine not to do it again before marriage.  Then you might do it again and once again determine not to let that happen again.  This continuing cycle is brought about by your being together in a marriage-like relationship without actually being married.  The temptation to sin is something all of us face as Christians, no matter how long we have been saved.  To “flee fornication” literally means to run away from the temptation to have sex outside of marriage.  Living together would only increase the chance to engage in fornication. 

Let’s also consider Romans 14:13 which says, “Let us not therefore judge one another any more: but judge this rather, that NO MAN PUT A STUMBLING BLOCK OR AN OCCASTION TO FALL in his brother’s way.”  A stumbling block is when we do things that might cause others to fall into sin.  If a weaker brother or sister in Christ witnesses your living arrangement, they may determine it is okay for them to live that way.  They may not be as strong as you and begin a sexual relationship without being married. 

Isn’t there a better living arrangement you can have until you are married?  I thank the Lord that you are looking to do the right thing in the eyes of the Lord.  His Word will answer your questions.  I trust you and your boyfriend can agree on this and, he too, will want to honor the Lord.  (CC)  (580.4)