endometriosis
"I loved how convenient this was, one shot every three months, but, look into ANY birth control before you put anything in your body. I thought all was well for about a week and then I started heavily bleeding. I bled nonstop for the whole three months, and my gyno told me that the bleeding wouldn't stop anytime soon, even if I switch birth control. I've read that the bleeding is caused by the progesterone only in the shot, so some women need an estrogen supplement or a different method of birth control that contains estrogen (I'm on the patch now) to counteract the bleeding. My cramps were not as bad on the shot, but, they were still there and occurred more often than before I started on the shot."