Hey there, okay thought I'd give this a go myself. Here's my question/Story
So I was dating this girl, we got together in January and we just broke up. She had a previous history of well cheating on her boyfriends, then leaving them for the guy she cheats on them with. I know because I was one of these guys as bad as I know that is. Maybe I deserved what happened to me.
Anyway when we got together we fell in love she told me she was crazy about me all the time, heck I fell so madly in love with her I proposed, and she said yes and she told me she would never do the cheating thing to me because she would care about me too much, far more than she ever cared about any of her other exes.
Anyway a few weeks before we broke up her best friend, a guy, who she admitted before having a bit of a crush on, had his girlfriend dump him. All of a sudden my girlfriend started hanging out with him a lot more often. Like, daily, for almost the entire day, he would stay over here a few nights.
Anyway suddenly she says we need to talk, tells me that she has grown unhappy with me and we break up, and it's just driving me insane thinking she left me for this best friend.
Am I just a suspicious jealous guy? Or do you think I'm right? I don't think I can truly get over her until I get over this but she would never admit it to me. I'm not good at arguing and she has always been able to turn any argument against me. If I tried bringing this up, I would just seem like an *** so is there any way for me to bring it up if it is true?
God this question is long I'm sorry, I just need to get this all off my chest before it tears me apart.

MAY have left you for him? The writing is on the wall. It's reasonable to be suspicious, which isn't even the right word since it's practically in your face. It's reasonable to be jealous, even though you fell for the same promises all the other guys had fallen for when you met her. (Having 'rights' to those emotions isn't really the right term; you can't sue her.)
Being dumped while being duped right in your own house hurts a lot. I would tell her that, tell your friends, tell her exes, but don't make too big deal about it because you have to accept it and get over it. It's just part of getting over the pain.

I just want her to admit it. As I said, she could argue and twist anything around. She is still living with me because she literally has no place to live right now. And once I can actually KNOW that she did, it will make me feel like 100x better...

Knowing that I was right, that her telling me I was crazy and that she would never do that stuff... It just feels like it would give me a damn good reason to move on, because right now I'm just stuck wanting her back.

Tec, there is a box at the bottom of the page labeled 'My Answer'. It gives you a lot more space to respond to the thread in.

I do not suggest telling anyone anything unless it is discussing your it with your best friend the way friends do.

A person who respects himself does not air his dirty laundry in the center of town. Getting revenge by dragging the whole thing through the mud makes you look as bad as her. Everyone already knows what she is like. Her friends and exes certainly should. You did, too. Whoever she plays with next probably knows the tune as well as anyone else especially if it is the 'best friend'.

Was this your place and she moved in? If so, she needs to find a place, yesterday. Work out the what needs to be divided up in the way of personal and community property and bills. Let her go stay with the best friend if he is that much of a friend. No need for you to play gracious host any longer than you have to.

You know her history. You ignored it when you were helping her cheat and 'move on'. Don't ignore it now. Accept it as the reason and let it go. Trying to get confirmation or build up resentment against her is only going to hurt you. Closure comes when you accept that reasons don't matter the results do.

Quite frankly, you have a right to be upset. You do not have a right to get self-righteous. Next time you get involved with someone make certain she is not involved with someone and have let go of her past relationships. Do Not get involved with someone who over-laps relationships. As you have learned, what you help do will end up being done to you.