Why Am I Not Bleeding After A Miscarriage?

hi,i recently had a miscarriage and i bleed for a day then stopped as i had a d and c.after 3 weeks the doctor gave misostopol to make me have a period but i didnt then a week later i was given folic acid...but til now 6 weeks later i havent had a period. am just having cramps as if am starting but nothing is coming out. i miscarriade when i was 12 weeks pregnant