Cheating

I have been dating my boyfriend for 5 years. I cheated on him twice in a manipulative friendship in highschool and he forgave me both times and stayed with me. Last night, he went to a concert, got drunk after I asked him not to drink and ended up making out with a girl, fingering her and having her stick her hand in his pants. I can't bring myself to forgive him, but I feel awful for not doing so. I just can't look at a picture or see him without crying and picturing the other girl with him instead of me. I don't know what to do. I love him, I hate that I love him. But I'm 1600 miles away from him at college and I can't build trust from that far away.