wow, I identify with you so much!!! Had close friendships crushes and what not but all 100% friendships and I felt feelings were mutual as happy to communicate but nothing that you can defy as romantic on purpose. I was in an all-girl school too.
Now I feel although model males in magazines - not any porn just ordinary magazines - who are heavy muscles but 100%shaved and have an ordinary good guy look - leave me indifferent. Female models - on the other hand, don`t. But If I sit in reality in front of an ordinary girl, or a guy - I prefer, usually the guy. Is this the same as you?
The funny thing about me is I always thought that certain female images turn me on because of identification. So never thought of myself as a B.I...but 100% straight.

I think that if you have a relationship that is valuable to you, on the personal level - stick to it whatever gender it is. We don`t HAVE to pursue both possibilities just because sometimes we feel like it? We CAN but how much does it matter? What really matters is not the word "straight" or "bi" but how you feel in reality.