Is this a miscarriage ? today ive been very tired and nauseous, i almost fainted earlier in the day. shortly after that i started bleeding heavily and cramping but its not a period. im on depo provera for 7 years and never bled on it?

If depo shots have been on time, it is 99% effective in preventing pregnancy. Something other than miscarriage probably is causing the bleeding. Any new, abnormal, or unexplained vaginal bleeding should be professionally evaluated, and nausea and "almost fainting" suggests pretty severe bleeding. Get care ASAP: if light headed or still feeling faint, go to ER or urgent care right now. Good luck.