Missing Periods--provera?

Hi. I'm wondering if anyone can give me some advice here. I've talked about this before, but I have more information now. I'm 18 years old, and started having periods at 10. By 11, they were regular (third week of every month). They are normally heavy and long. My last period was the third week of july. At first I thought I was pregnant, but the doctors ruled that out. The first doctor I saw gave me provera pills for 7 days and said that should start my period. She said the problem was stress from coming to college. After taking the pills, nothing happened, so I went to a different doctor. He ran several blood tests, and said all my hormones were at normal levels, and he didn't know what could be causing my problems. He referred me to a gynecologist, whom I saw friday. The gyn said that he thinks I may not be receiving the progestin trigger (whatever that is) and that's why i'm not having periods. He gave me 14 days worth of provera pills, and said it should start my period. He told me that if it doesn't i'll have to try estrogen pills next, to see if that's the problem.

My question is, is that possible? Could my hormone levels be normal on tests, but still not work correctly? And wouldn't the first round of provera have fixed it?? I thought that those hormones only got screwed up during menopause...But i'm too young for that. What could cause me to suddenly have hormone problems after 8 years???

Daile