There've been a few times where I've been in basically the same situation: going a while without much face-to-face interaction with people, and I start to think that I might be bi because men seem attractive in fantasies, or in anime or books. But then every time that's happened, the next time I actually interact with another man in person I instantly "snap out of it" and start wondering why I ever thought I might be attracted to men. There's just something about in-person interaction that makes it different (my guess is that it has something to do with pheromones, but I don't actually know).
Of course, I can't speak for your situation. Maybe you're actually bi and just realizing it now, maybe you're not. Either way, I wouldn't worry about it too much. Just pursue whoever you're attracted to regardless of gender, and remember that sexual preference is only a description of who you find attractive, not a rule you have to follow. I'd also like to say that I think >>3272
is horribly over-analyzing this situation.