You definitely need to figure out what caused the original breach in your relationship and you should be able to talk about the things that concern you, in therapy. Sex is important but it sounds like communication and intimacy are things you need to work on as well. It would be great if he forgives you but I think it would be dangerous to forget it happened because it may manifest it self in other ways. A little guilt is also not a bad thing as long as it does'nt turn to hopelessness. Stay with the therapy but you need to insist on dealing with the issues that bother you. And keep posting on PC!