I need some help with my menstrual cycle?

I don't have a period because of certain medical issues and I am now trying to get pregnant, I have never had a natural period but because I still get the pains and the blood builds up every month it becomes unbearable sometimes, I have now been placed on medroxyprogesterone and I need to take them every two months for a period. I am now trying to get pregnant but how am I supposed to know if I can get pregnant if I don't have a regular period and if I don't know I am ovulating? Please help.

Don't get medical advice from people you don't know on the Internet and have no idea of what their degree of expertise might be. Those are all questions for the doctor that prescribed the medroxyprogesterone.