Shooting pelvic pain when urination and bowel movements. irregular period. back pain all the time. what could this be?

A few things: Need more info but a few things to consider: endometriosis, sacral plexus nerve problem, polycystic ovaries. Endometriosis is a disease where endometrial lining implant anywhere in abdominal cavity. Causes irregular periods, a lot of pain which you seem to be having. Might be worth having a chat with your dr for investigations.

Needs evaluation: Suggest that you should be evaluated by your Primary Care Physician.