I think it really depends on where you live - the last time I knew, if you're a minor and have a sexual relationship with an adult, the adult can be charged with statuatory rape, even if you gave him consent to have sex with you.
I can't stress this enough...If you don't want to get pregnant, utilize as much protection as possible. Birth control, condoms, spermicide, intra-uterine device (well maybe not this one because it's so expensive), whatever. But it's good that you are using some protection now...Always be careful.