Taking MEDROXYPROGESTERONE BRAND NAME(S): Provera

Okay. So my question, is I have been taking this medicine for over 3 years to to have my monthly since I do not get a P. My Dr said I do have PCOS.. and I take pregnitude, 2x a day.. but recently I took the provera, for my normal 10 days and no P.. yet... I took a test before I started the meds and it was negative, but now I'm beginning to wonder..any advice wold be much help. .?