When I was 14, I was a Christian and had a boyfriend who was a Christian as well. One day we messed around a little with sexual pleasure but didn't go all the way. After it happened, I asked God for forgiveness and felt terrible. We ended up doing it repeatedly.
After we broke up, I wanted to start fresh, so I repented of the sexual stuff I was doing before marriage.
Now I'm in a relationship again with a boy, and I'm now 15. This boy and I did the same thing I did with the other boy. I asked God for forgiveness because I felt so terrible. I even promised God I wouldn't do it again. But I did it again, and afterward I asked God for one last chance. I ruined that one last chance, and now I feel the worse I've ever felt.
I've read in the Bible that fornicators aren't going to heaven. Have I lost my salvation? Will God ever forgive me? I actually do want to stop this sin because of how much it hurts me and God. Is my heart going to harden? Are my relationships going to be ruined? Should I break up with my boyfriend? By the way, I've already told him that we can't do the sexual stuff anymore because I'm disobeying God. I don't know how to erase this guilt and shame and just start all over again.
Even when intercourse doesn't take place, you could be involved in fornication. For instance, mutual masturbation is still considered a form of fornication. And this wasn't the only sin taking place. You and your two boyfriends have been involved in lewdness (making out), lust, and sexual touching (Mark 7:21-23; Romans 13:13-14; I Corinthians 7:1). None of you are behaving as a Christian should behave. "Now the works of the flesh are evident, which are: adultery, fornication, uncleanness, lewdness, idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies,envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God" (Galatians 5:19-21).
Promising not to sin is foolish. You are already required as a Christian to not sin. When you promise not to sin, you are basically telling God that His Laws really don't matter, except when you think they are important. You are not in charge, God is.
All sins are forgivable, if you turn away from the sin. While you intend to not sin, you have never really left the sin behind. The only time you stopped was when you didn't have a boyfriend tempting you to sin. No one is going to make you stop sinning. You have to choose to walk away from the sin -- even if it costs you your relationship with a boy. Thus, it is not that you have to leave your current boyfriend; it is that you are committed to serving God, so that if a boy touches you in appropriately that you walk out, regardless of what he says or how you feel. "For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death. For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter" (II Corinthians 7:10-11). The reason you continue to be weighed down by the guilt of these sins is because you never proved to yourself or others that you won't participate in them.
Of course, if you keep on sinning over time you are going to find excuses why those sins are not so bad and your heart will become hard. The solution is to change now, while you have a desire to change.