Havnt had my period for several months

I am 17 years old. I have had sex before. I havnt had my period since August 2005. I dont have any of the symptoms of pregnancy, and I have taken several pregnancy tests, all different brands, and all have came back negative... any ideas? or other signs I should look for?

Pregnancy tests are not always right I say you should go to the doctor because if your not pregnant then there could be something else wrong so go to your doctor

Honey, you'd know if you were pregnant by now. I mean seriously, don't you think you'd be showing? And it almost never happens that pregnancy tests come back negative when you are 3 or more months along. So, think about other reasons to not be having your period: it happens for many girls who have lost or gained a lot of weight in a short period of time, girls who exercise a great deal, those under a lot of stress, or infections or other medical reasons. You aren't pregnant, there's some other reason for this that you should see a doctor about.

It's been 8 months, it's time to see a doctor to make sure nothing is going seriously wrong in your body...