Bisexuality Support Group
Bisexuality is a sexual orientation which refers to the aesthetic, romantic, and/or sexual attraction of individuals to other individuals of both their own and the opposite gender or sex. Most bisexuals are not equally attracted to men and women, and may even shift between states of finding either sex exclusively attractive over the course of time.
I think it is a rather common phenomenon that women's sexual attraction is more fluid, as the above article indicates. So, there is nothing wrong with you. My former wife had changed her sexual orientation and so I do know that it happens.