I had sex with an ex-girlfriend this past weekend. There are quite a few things I don’t understand.My ex-girlfriend and I broke up about 3 years ago when I was a senior in college. She has cheated on her two boyfriends that she has had since we broke up, with me. She claims that the guy she is with now is possibly the guy she will end up marrying. She tells him that she occasionally talks to me, but in reality she calls me a few times a week and text messages me almost on a daily basis.She is the one that invited me to a friend’s beach house this past weekend, where we had sex. After she has been drinking she asks me questions like, ‘Why were you so mean to me when we were together ‘ and ‘I wonder what things would be like if we were still together ‘. Most of the time when we talk, we talk about sex, but this past weekend was the first time in a year and a half we had sex.We had a great sex life when we were together, but she also says she does now too with her boyfriend. I have yet to find a girl who I enjoy spending time with as much as I did with my ex-girlfriend.Since we have been apart I realize that I didn’t treat her as well as I could have and wished I had told her how much she did mean to me. I often ask myself if it is possible I still have these feelings for her, but I try not to think about it, knowing she does have a boyfriend.Sorry about the length of my story, but I just wanted you to understand why I have these questions. Why does she keep in contact with me? Why did she cheat on her current boyfriend with me, when she says this could be the one she marries?I always tell her she must be missing something in her relationship, if she does these things. I tell her if she is as happy as she says she is then she wouldn’t think twice about me or jeopardize the relationship like she does. She replies that she is happy and this is not true at all.I came very close to asking her back out about a year and a half ago, before she started dating her current boyfriend, but the opportunity slipped by. I believe she had a feeling I was going to ask her out again and she would make comments around me like ‘my parents would be upset if we dated again’ and ‘It just wouldn’t work out’.I have apologized for the past, I am just so confused. I know she does care about the guy she is with now, but she is sending mixed messages. I really don’t think she knows what she wants. I’m not saying I think she wants to be with me, but I just don’t understand.If you could offer any kind of advice or feedback, it would be much appreciated.