It sounds like you had as much right to find happiness as your boyfriend. So, try not to feel guilty. You were making an effort to be open and honest with your boyfriend when you told him but he reacted in anger. If any relationship is going to thrive, honesty has to be there. I would wait until your boyfriend is not as angry and try letting him know that you wanted to be honest with him and did not want to hurt him. He was not there with you in a committed situation and you had every right as an adult to do as you choose. Be honest with your boyfriend and let him know your reasons...perhaps you were lonely as is often the case. You can also let your boyfriend know that you weren't trying to cause him pain with the situation since it sounds like that was not your goal. Issues like these can create problems in a relationship if they aren't resolved. If you two are able to talk it out, I'd suggest making an agreement that neither of you bring up past situations in the future because it provides fuel to fire arguments. That's with the understanding that both of you are able to express your feelings in a discussion and get them out in the open (take time to talk it out once not over and over again.) Perhaps he was hurt by your actions but I'm sure you experienced hurt as well when he chose to be with his ex-girlfriend. Hurt happens because we are human and have feelings but we can heal from it. If things from the past are brought up again and again, it is like opening a wound again. Deal with it now and put it to rest. If he cares about you, he can find a way to forgive you. Focus on the fact that you weren't out to hurt him and were simply feeling lonely or whatever it was you felt. Apologize sincerely ***** *****'t feel bad about yourself or harbor guilt because it isn't healthy. Don't allow anyone else to make you feel bad either. Remember, forgiveness can take time. If you both plan to remain committed, stand by that now that you are. Make a mutual agreement not to engage in sexual activity outside of the relationship to provide a sense of comfort/reassurance. Best of luck with your relationship!