I have a question regarding confession. Recently my ex-girlfriend's parents have asked us to break up because they want her to wait until she is 18. We have reluctantly agreed and are now just 'friends,' as best we can be. But at times we have slipped up physically (well, kissing and heavy petting) after her parents have told us to break up. We have realized it is the wrong thing and asked forgiveness with God and will not do it again, however hard it is. I feel really bad because in some ways we have dishonored her parents by being physical. They do not know about it, and I think telling them would cause a lot of harm. It would cause a rift in my friendship relationship with her and cause harm to my relationship with her parents. We are trying very hard to honor them. Do you think I would need to confess this to her parents, or can I move on and insure it won't happen again.
The reason her parents asked you two to back off is because they are concerned that she is not yet mature enough to tell you "no" if you push this relationship toward sex. I know that this is not your intention, but clearly her parents are justly concerned since even after agreeing to be just friends for the time being you have been acting sexually with each other.
Young people understand that sexual desire is strong, but they often don't realize how strong it is because of their lack of experience. Paul stated that "Now concerning the things of which you wrote to me: It is good for a man not to touch a woman" (I Corinthians 7:1). By "touch" he is referring to sexual touching, which is what you have been doing with your heavy petting. The reason it is wrong is because it stirs a passion for sex, which cannot be legitimately fulfilled because you are not married. When people are sexually aroused, they don't make good decisions. The judgment centers of the brain tend to shutdown and instinct dominates. They know that you have no intentions of committing fornication, but when it comes to sex, intentions aren't always followed.
It is your intention that this behavior will not continue, but I can't help but notice in your note that you aren't certain you will be able to stick to your intentions. That is actually a sound way of looking at the situation. It is when you are convinced that it will never happen to you that you drop your guard and it does happen. "Therefore let him who thinks he stands take heed lest he fall" (I Corinthians 10:12). You have to accept the fact that you are male, that your body wants to have sex, and if you are not careful you can easily give in to temptations like fornication; just as you've already gave into lust and lewdness.
One of the "gotcha's" about sin is knowing you are going against the rules is exciting and makes sin even more attractive, even while your mind is telling you "we shouldn't be doing this." "Stolen water is sweet, and bread eaten in secret is pleasant" (Proverbs 9:17). It is the fact that her parents said, "no" that causes it to be more of a temptation to do things you both know they won't approve of.
The sin you were involved in was technically against yourselves. "Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body" (I Corinthians 6:18). I'm glad you repented of it. There is no requirement in the Bible stating that you must tell other people that you sinned unless you harmed them in some way. There is encouragement to talk to other Christians about the problems you are facing, just as you have come to me with your problem. "Confess your trespasses to one another, and pray for one another, that you may be healed. The effective, fervent prayer of a righteous man avails much" (James 5:16). So, in this case, there isn't a reason to tell her parents what happened or almost happened.
However, you need to put strong measures in place on yourself to avoid similar situations. You need to make it a rule not to be alone with your girlfriend. No going to each other's place without someone being there. No going off to places where it is just the two of you. Knowing that someone could walk up on you at any moment will be extra encouragement to keep your hands where they belong.