Why Am I Still Having Heavy Bleeding And Pain Months After A Miscarriage, With Positive Pregnancy Tests?

Hi I have a big problem I got miscarriage on December I consult with the docter and he give me the pills since December until today now I m still bleeding and a heavy bleeding with pains when I go to my doctor he don t know what to do anymore because when he scan me he said there is nothing in my stomach but bloodtest with pregnancy test are saying that I m positive I will appreciate if you can help me because I always have this pain like I m going to give birth