I was on the depo shot for 5 years. I went off in June and have not gotten my period back. Today I have been experiencing severe cramping almost like labor pains. I am not sexually active, so I know that I am not pregnant. I have been taking Advil which makes the pain go away, but an hour or two later, it is back. What could be going on?

I had something similar. Doctors say that after being on the depo injection for so long, it can take some up to 3 years to get their periods and fertility back to normal. This is why it isn't a recommended contraceptive for couples looking to conceive in the short term.
I was only on the depo for 1 year, and it took me 3 months for my period to come back. It will just take some time. Your cramping will be due to your body's reaction dealing with the new hormone changes. It is nothing to worry about. If they persist for much longer, or the pain is still at a high level, see your doctor. However it sounds to me it is just one of those "woman things" unfortunately! Good luck. Hope you regulate soon!