Search Results: taking sides in a fight

Just a basic question, in my experience my current girlfriend was talking to another guy behind my back, she was gonna go to a bar party with me for an event but I ended up not being able to go, she ended making a plan to go to a guys hotel room instead & I found out, we fought & we broke up that night & she tried to get back together again the next day, then the same guy invited her to a pre-game Christmas party & she said she was going & I told her I was uncomfortable, they showed up to the same bar together & I beat him up (wasn’t a good idea), she ended up sleeping with him that night (I know because I showed up to her house, they were both in their underpants when I showed up to her house for my clothes I’ve lent her) after the night at the bar. She tried taking me back the next day (& It’s a little gross I was with someone else & got her to answer the phone for me to say I’m busy lol) & I ended up taking her back. She being saying we weren’t together when these things happened for months but I still feel cheated on & betrayed & I don’t know what to do how to approach the situation because she doesn’t let me talk about it & says it’s a long time ago & pushed my feelings about it to the side for half a year & I’m very unhappy with her (but I’m more scared of being unhappy without her). Since the second issue happened I’ve been less committed to her & flirting with other girls & making new relationships (I have not had sex, kiss or physically cheat) because I don’t feel safe or happy in my relationship & she’s trying to tell me that me flirting with other girls is cheating though. I’m just wondering if what she did would be cheating because she says it’s not & expects me to forgive her for it but I don't know how too (& I feel more foolish by the day)?