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.

What you describe is the same exact thing that probably 75% or more of gay/bi people go through. It is completely normal to feel the way you do. You may be closer to gay than bi, but only you can decide that. But I think you have probably realized the most important part, that is realizing that your feelings for the same sex, is more than just a passing phase, it's who you are. Maybe your bisexual, maybe your gay, only you can decide that, but your ahead of so many other people right now.
Find a lesbian organization, or maybe make friends with that girl at school/work that everybody is pointing at and calling a dyke. Meet some other girls, find out just how strong your feelings for girls is.