You haven't made enough changes if you are still hung up on her. You need to completely let ago and truly become comfortable with living on your own, and then really move on. The fact that she moved on quickly shows that she was ready to move on for a while before actually breaking up with you. Even though you have made a lot of improvements, she is unlikely to give you another chance because she moved on. You need to learn from your mistakes and then get a fresh start with someone new.
And if all the women you've been meeting are just into partying or casual sex, then you need to find a new way to meet women. I'm not personally religious, but I've heard that the young women at church tend to be normal and not uptight holy rollers, so maybe you could start showing up on Sundays. Or do some volunteer work. Get involved in some co-ed recreational activity like volleyball. Whatever, don't just look for women at the bar or at parties.
Good decisions come from experience. Experience comes from bad decisions.