I sort of told everyone at school we were dating. Then she said we werent?

I have been going out with her about 2 times a week for about a month and a half. We've even gone all the way about 6 times. I told people we were dating and she found out and got mad and said we weren't. Now I think she is dating other people on top of me. Why are women such tramps and how do I get revenge? Really, though, have women gotten so loose with their morals that they think this is okay?