Honestly? Not until high school. I was always pretty hetero as far as I knew. I related to the other girls and when they talked about romance with guys, I could relate because I too liked guys and for a while, my crushes were only guys.
I met this really pretty girl and I thought I just wanted to be her friend until I realized I felt the same way about her as I did my guy crushes. Fortunately, she was a lesbian :)