If you have insurance or can afford it, I would strongly suggest seeing a specialist, specifically a Reproductive Endocrinologist. They specialize in infertility and an run a whole lot of tests to see if there are any issues. At least having the basic tests run can give you a wealth of knowledge about your fertility. Could be something "simple" hindering your fertility or something that may take more work. Most gynecologists and primary care doctors can run these tests too if seeing a RE is not feasible. This would be blood tests to measure your progesterone, thyroid, prolactin, etc. It was actually though my gyn that I learned I had a thyroid issue. Still not pregnant but we are slowly working on fixing that. Good luck!
Im having the same prob. Depo is the devil alot of people say take the pill to regulate your cycle but to me it could be worse cause your putting more hormones into your body i been trying to conceive for about 4 months now your not alone ...