Am i bi, a lesbian, or hetero?

because at school (i'm 13 & a girl) sometimes if a girl has a really low- cut shirt or really tight stuff i'll stare at her, wherever it is... but then i find boys attractive... and i have a few crushes but only on guys! honestly you people will say "oh you're too young to know about your sexuality, bla blah blah" but i don't care because i'm kinda worried that some friends and other peopple will maybe end up picking on me if i'm a lesbian or bi! i don't know what to doo... :'(