I'm on provera (medroxyprogesterone) and I want to know how long does withdrawal bleeding last? And im having right lower back pain and right side pelvic pain.

Typically . Typically Provera (medroxyprogesterone) is given for a week to ten days; after it is taken usually within one to two weeks after stopping it the withdrawal bleeding starts. If the withdrawal bleeding starts while taking the Provera (medroxyprogesterone) it can be stopped. To answer your question the withdrawal bleed can last anywhere form 5-10 days or so. If it goes on longer than this you should consult your doctor. Also since you are having pelvic pain you should follow up with your doctor right away. Take care.
Varies. It depends on how long you had not had a period, and how thick the lining of the uterus had gotten. If it had been months and the lining was thick the withdrawal bleed can last a long time.