(Really long!) Is it a phase or I am unable to accept myself?

I wouldn't be so concerned about labels... you can't help who you are attracted to! It doesn't matter if your "straight" or "bi", not everyone fits into categories. You can call yourself whatever you feel most comfortable with, but don't stress about it! You're still young and figuring yourself out, there's no need to be ashamed for who you are, even if you don't know who that is quite yet.