I am also 19, I wiegh around 157 lbs...and my periods have been going on for 8 months too. I was 11 when my periods begin and had very horrible cramps and was put on the birth control pill, around the age of 13 or 14..my body reacted to the pill great and my cramps went away, and also had periods that lasted about 2-3 days at the most. Just recently last August I began the Depo shots I recieved 2 shots and my period hasnt stopped but only for 2-3 days every few months. After I reached 6 months of having a period..I decided to go back on the pill. I am cerently on my second pack and they still haven't stopped. I went to the Dr.s' last tuesday and they said "Finish the third pack, If they haven't stopped by then; we'll talk about other options. I was wondering if you ever found out what is causing this to happen to you??