How come my mom wont let me date and live my life?

im 16 and my mama say that i cant date until im 18 because i might bring Some one crazy home(i could also bring someone crazy home at 18)..she let my brothers date when they were freshman's in h.s (I'm a junior) and when they came home saying they weren't virgins anymore my mama didn't scream at the or nothing she just said"was it good and were you protected".but she would have a fit if i came in the house saying i kissed a boy..and she says i should wait til im older to get a bf because i shouldn't be having right now and that's what a bf would want and that if i get pregnant the bf most likely won't help take care of the baby and i will be on my own..she also thinks nobody out here is worth me........BUT SHE SAYS SHE TRUST ME TO MAKE GOOD DECISIONS AND OUT OF ALL HER KIDS I AM THE GOOD CHILD...SO SHOULDN'T SHE LET ME VENTURE OUT AND MAKE MY OWN MISTAKES AND LIVE MY OWN LIFE!!! SN:Idk HOW TO TELL HER ANY OF THIS IF ANYONE HAS SUGGESTIONS HOW THAT WOULD BE NICE..BEST ANSWER 10 POINTS