Cheated on would you stay?

An affair may be a cry for help, a catalyst to start talking honestly. So I'm not sure if i would stay or not.

This exact thing happened to me. I suspected that my live-in boyfriend was sleeping with a coworker but he denied it, even swore on his 2 little boys' lives that he didn't. I had seen suspicious text messages, he invited her and her kids over for a party that he knew I'd be upset about (and asked them to stay when I decided to leave for the weekend), he'd stayed out nights at events I knew she was attending and she was furious when I showed up at his Christmas party with him, so I was within my rights to be. Everytime I asked, he got more and more upset and even had the nerve to deny it again the day she told me. When I told him she described his, err, genitalia, in a way I would say was eerily accurate if his story was true, he finally admitted that it had happened -- once. Not her story, but I was sick of fighting with him about it. A few days before Christmas, she called to tell me that he was trying to have her fired for harrassment, and felt I should know the entire story. I was livid. I couldn't believe that he'd denied it for as long as he had. I stayed with him, not because I wanted to be with him, but because I needed to stay in the house we rented together, and my landlord convinced me to hold my ground and get him to leave. It took a LONG time, but he did eventually just up and leave one month. In hindsight, I wish I'd just called up all the friends that offered to kick his butt for me and force him to move out right away, but since we also lived with his coworker and best friend, it probably would have made things really awkward. It's the entire reason that I won't move in with another man until we've known each other for a long time, and he's proposed. I want proof that he's committed, not just some guy looking for a live-in housekeeper and cook.