How do i explain to my parents that im old enough????

my parents dont understand that in old enough to make my own desistions. i am 17 and they think that when i wear makeup that i look like a skank and that its ment for sluts who are up to no good.(as a nice way to put it) my boyfriend and i want to spend time together but we are always being watched. they dont beleive me and anything that i do. they think that ill end up like did having a kid before in out of high school and then have a nother one a year later. i need help... they just dont understand.