Pisces boyfriend cheated with a Capricorn?

My Pisces boyfriend and I had just gotten back together that day, and that night he went out with his friends to this Cappy girl's house. I don't know much of what happened, I just know from his phone that they "did some kissin". (I know I shouldn't have gone through his phone but, hey, I'm a Scorpio). He told me they did nothing. I told him what I had found out, but I chose to forgive him because we had originally broke up because he suspected me of cheating. I never actually cheated on him, but he thought I did so even after we reconciled our differences he was pissed off, and got drunk and kissed this Capricorn chick. Was I wrong or right to forgive him and stay with him? He seems to think we can't get out of this rut by I have faith our relationship will work with a little time. Am I sticking to this too hard due to my Scorpio tendencies? I'd like some insightful responses, not just to tell me to leave him. Thanks guys :)