what should i do with my crush?

I (M15), have had a crush on a girl for three years (F15), but weve only started talking about a year ago, this is the last year we are together in the same classroom before we go to different highschools, i dont know what to do, if i tell her, it wil not be mutual and she will reject me, making things uncoftormable and we will probably stop being friends, but if i dont tell her, i will regret it almost all of high school, what should i do? (update she said no) but at lleast were still friends so bright side