I don't really understand some feelings i have about some things in my gf's past?

HA, man i feel that pain. I have never had a girlfriend like that, but i do LOOOVVVEEEE those girls that are pretty good until you get them out and they get WILD. it's a guy thing i think. If her cheating doesnt bother you then the hell with it. sounds like you got a keeper to me. Maybe not one to marry, but atleast to have a DAMN good time with.