Suggest Treatment For Prolonged Vaginal Bleeding

Hello, I am 25 with a history of PCOS. I take ovcon 35 and Agestin to keep me from having periods each month and I have now been bleeding for 3 weeks I had an ultra sound done on Tuesday which did not show and cysts at the time but I can not get the bleeding to stop or the cramps, which is my reason for being here because the cramps have been so bad that demerol is not even helping at this point. What is causing this and what should I do? I'm miserable...