I'm not sure how to help with your problem of meeting girls (although I think chatting them up at parties is probably a good way to get started), but you have to do something about this arrangement with your ex-gf. I know it's not feasible to have her move out, but the set up has got to be made more agreeable than it is now. You have to talk to her and lay down some rules, as in "no dry humping/making out/whatever in common areas". For her to do that is just disrespectful and frankly, quite slutty. And take it from me, as I've been a girl for nearly 25 years now , she *wanted* you to hear her getting it on with the new guy. Heartless bitch.