I agree with the others, your body must not be ready to be pregnant... because I'm sure you would have gotten pregnant by now! I know a girl who is actually still a virgin and got pregnant. Her boyfriend ejaculated outside of her body and never actually went inside of her and she got pregnant still (how rare!). Just be very careful and try waiting for a while. You should use protection meanwhile to protect against STD's since it's easy to catch one that never shows any signs.
Just make sure you are definitely ready for a baby before you start trying! I would hate for you not to be able to finish high school because of the baby. Plus, make sure you won't mind having to stay home and not go out and do fun things and have to change poopie diapers! It's definitely lots of work