Abnormal Menstrual Cycles, Severe Hip And Back Pain Before Cycles. What Is Going On ?

I have very abnormal menstrual cycles, often missing months between cycles. For about a year and a half I was on the pill, but got off of it last June in order to start trying to conceive. I got my period for the first time almost exactly a year later, two weeks ago. But before getting my period I started having severe hip and back pain. I have had my period for two weeks now with no clotting, which for me is abnormal. What might be going on?
I've had hormone tests and ultrasounds before and all of that was normal.