I have begun to have abnormal menstrual periods after stopping the Depo-Provera provera (medroxyprogesterone) shot in 2010. And now I am unable to get pregnant. What can it be?

Needs evaluation. The effects of depo-provera on your body have been out of your system for at least two years. If you've been trying to get pregnant all of this time and it's definitely time for a fertility evaluation. A young healthy couple should try for one year before pursuing this option.