First of all, look at your behavior in all your relationships. Are you the type who tends to get insecure? If not, then maybe you have reasons to be suspicious of her. Don't ignore your gut instincts. But if you tend to be clingy, jealous, and insecure then maybe relationships just aren't your thing. You may need to grow up a little bit (and I don't mean to be insulting when I say that) before getting involved with anybody.