I wish I wasn't like this..

when im with someone in a commited relationship I flirt with other people :( . I also usually find a next before I leave someone. I've had a bad past also an over whelming fear of being alone. I believe its to do with alot of rape and molestation that has happened to me. I dont open up after my first relationship because it lasted years, I burned badly burned with that one. I feel like a dirtbag about being the way I am :/ .