Girlfriend Cheated with Several Larger Men and I Can’t Confront Her About It

My gf Katie and I are a young 20’s couple and I recently found out she cheated on me a lot…  I always knew my gf was a little bit of a slut, she was often the type of girl who ended up naked at the party or would make out with girls, I never knew how bad it was until the other night.

We were all drunk and her friend dared me to let her fuck this guy Caleb.  I agreed as long as I could fuck someone too.  

The four of us went to the bedroom and Caleb started eating my gf, Katie, out.  He did things with his tongue and fingers I never knew how to do and she squirmed and moaned a lot.  Then she pulled his boxers down and sucked him hard, he was a good 8.5 inched, but really thick.

At best I’m 4.5 inches and not that thick…..  

He fucked her really hard and she screamed louder then I had ever heard…. The whole time I was trying to fuck a girl but couldn’t get it up. I was so turned on and so humiliated watching my gf get pounded to ecstasy.  After they finished the girl I was with gave up and left and my gf just lay there, her pussy was really swollen..

I got really jealous and begged her to fuck me now since I hadn’t gotten it up earlier… Eventually she gave in and rolled on top of me, she didn’t really fuck me though, I more just had to hump her while she lay there.  She was really drunk and started mumbling to me how she’d cheated on me before and kept it a secret.  

I found out there had been 7 guys she had fucked regularly behind my back and a handful of others she had either screwed at parties or fooled around with just a little for fun.  

The next day I went through her phone and facebook and found out she was telling the truth. I can’t confront her about it though…