Your best bet is to take another pregnancy test, but if you had a period and it was prettymuch normal, you're probably not.
I don't want to sound like I'm preaching to you or anything, but If you're not pregnant, try to be careful next time!
It's dangerous for you and the baby to be pregnant at such a young age... your body is not yet fully developed and the risk of preterm labor and miscarriage is very high if you are under 19 years. I had quite a few friends in high school (which wasn't long ago, I'm only 21) that got pregnant, and none of them had normal pregnancies.
I'm sorry, I'm not trying to scare you... I just want you to know, in case you aren't pregnant, so you'll be more careful next time.
Anyways, get tested and if you are pregnant, just take care of yourself. Let us know how the test comes out.