Currently on depo provera, (medroxyprogesterone) yet each time after having an oragasm i have very light bleeding, then it decreases again. why does this occur at that time?

Contractions: An orgasm is basically a contraction of the uterus and when that occurs sometimes a little blood can come out. Bleeding can also happen after intercourse from fragile blood vessels on the outside of the cervix if you hare having penetrative (penis inserting in the vagina) sex. See your doctor if persists for pap smear to make sure no lesions are cause of bleeding on cervix.