unprotected sex always carries a risk of pregnancy, however, it's puzzling that all your pregnancy tests have come up negative.
Since you havent had your period for such a long time, a pregnancy test shpuld've picked it up. Why don;t you visit a gynecologist or take a blood test? can u visit planned parenthood or something similar?
In the future please be careful and educate yourself of all methods of contraception.
Wish you the best and hang in there- don't be afraid to confide in your parents! thye;ll do what is safest for you! keep us posted.