"I cheated on my boyfriend with my ex," said the woman filled with regret and confusion. Familiarity can be a good thing but it can also be a horrible thing. Perhaps you felt so comfortable being intimate with your ex again because you knew him so well. Maybe he turned on the charm and a bunch of old feelings flooded over you and you felt drawn to him. Regardless of why it happened, you now have to deal with the consequences of your actions. If your current boyfriend has found out that you slept with your ex, he may not want to remain your boyfriend for much longer. Unless you do some dramatic damage control, you may find yourself alone and wishing you could turn back the clock and undo the dreadful mistake you made.
Since you cheated with your ex and thought infidelity into your current relationship you have to have the one to bear the blame for the problems you are facing now. Trying to explain away your actions by saying that your current boyfriend was not spending enough time with you or you felt unappealing to him will not cut it. You made the decision to be unfaithful and you have to own up to that. You can begin to do that by being as honest as you possibly can with your boyfriend. Answer any questions he has in the most sincere manner you can. Do not try and hide behind a veil of tears and do not point the finger of blame towards him. You need to be mature and respectful of his feelings. You messed up and you can not forget that.
You also have to take the step of breaking off all further contact with your ex. It's disrespectful to your current boyfriend for you to continue to have interactions with your ex. That means you can not email him or call him anymore and you definitely can not see him. The man has become part of your history. Be clear with your boyfriend about your intentions to push your ex out of your life. He'll take comfort in knowing that you're making that sacrifice for him and it will help him feel important to you.
One big part of healing a relationship after cheating has occurred is rebuilding trust. You need to work hard at that and be patient as you do so. Your boyfriend is probably going to want access to your cell phone and he may even ask for your email passwords. You may feel that this is an invasion of your privacy or personal space but consider his side in things. If you grant him more access to your life it will help him to feel he can trust in you sooner and that's an important step in rebuilding your relationship.