What Causes Smelly Vaginal Discharges?

im 16, 5'5, 145 lbs, been pretty healthy all my life nothing out of ordinary in ANY of my regions. recently ive been on pills that make me not eat or sleep (but i do drink a dickkload of water), i dont know if that has anything to do with my question but whatever. i also had my first depo provera around three months ago (i havent been keeping track of the time, it could be more or less) but i think im overdue for the next shot. so lately ive been having brown/black discharge that smells bad. it looks kinda like shitt but i knoww its coming from my cooch, so whats going on?? if you knoww. its starting to trip me out. thanks<3