so my girlfriend of about 3 years decided a month or 2 go to start cheating on me with a guy from work. she was constantly texting him, lying to me about who she was texting etc, saying she was talking to her mom, best friend etc. called her out on it, we had a huge fight for like 4 hours with me asking to see her phone. i said "honestly if i were to look at your phone what would i see" she made up a whole bunch of lies of course, i asked if i could see it, her demeanor totally changed, she was defensive and aggressively attacking me as a person. ended up she got caught in the lie, confessed to liking him and going out with him a few times etc, of course i had my doubts.. 2 nights ago when my gf fell asleep i popped open her ipod touch to look at her facebook, i hadnt been able to sleep well since the first instance, too many thoughts in my head, she has been distant for a while now. at first when i read her message to her friend about how much she likes this guy, and how even he seemed to vilify her for cheating, saying something about "even though you would cheat on me you would still be my little nerd girl" i was crushed. our relationship has always been up and down, but at the end of the day we were always there for each other, we both have our own demons. the thing that bothered me the most about her message was that she told her friend the only reason she hasnt broke up with me is because she pities me for being in a slump (car wreck, injuries, sisters house burning down etc.) that hurt the most. so after a whole day of her texting me that she still loves me and wants to make it work, try again in the future etc. i write it off as her just trying to make me not so down on myself. im a pretty big alky, but have always managed to hide it from her for the most part.. the second i got off work i started drinking, texted her to come pick me up and talk, i told her everything how i feel, she layed on my held my hand etc. after i said my peace she invited me back to her place. she felt just as distant as she did the entire time before, no remorse, no makeup sex, hell not so much as a sniffle. theres no regret. then it hit me, she has cheated on every boyfriend she has ever had. this WILL happen again in the future if i stay with her. any girl who can justify cheating on someone and feel no remorse about it will surely do it again.. in a sense i regret staying over, i dont want to be with her anymore, after my catharsis i feel like i have a clear head. i dont want to force myself into her life, id rather be by myself. whatthe fuck should i do?