What Causes Sharp Pains In The Abdominal Area?

I haven't recieved a period in december and on january 4th I had light spotting. I went to the doctor and she prescribed me Provera to take for 5 days. It is now january 31st and for the past 2 days I have been having sharp pains in my abdomial area. It starts off sharp and goes dull. I have been spotting and bleeding for 24 days now. I have very sore nipples. Its jus the nipple part. What's the problem?