What's going on with my uality?

So I've had crushes on guys for all 3 years of high school, and i was really infatuated with a guy last year! I fell in love with a guy and he didn't feel the same, and it took me almost 8 months to completely lose my feelings for him :( it was really tough, and when i finally let go and just accepted our friendship, i felt this strength and i just felt no desire for guys as a whole. not just for him, but for guys as a whole. then i started feeling romantically attracted to girls, and my romantic attraction toward guys went away! What is going on? I'm really scared. i miss being attracted to guys, but now whenever i see a girl at school i imagine myself being her boyfriend (holding her, buying her flowers, etc), and it's shocking because that's what i always desired in a boyfriend & for myself. but it's like now i have a desire to Be that boyfriend/girlfriend for girls. what does this mean? what should i do? i used to always fantasize about falling in love with a guy and getting married, etc, but it's just not there anymore. do you think it's just a phase? thanks!