I Am 16 Years Old And I Was Put On

I am 16 years old and I was put on the depo provera shot to stop my irregular periods. I also have a boyfriend and we happened to have had sex a week after I got the shot ( we used protection ). My period was stopped then for a whole month. It is now my second month of depo & still only had one shot and I am bleeding like I am on my period, just as bad, but it does not smell like period blood. What is wrong??