I have had this all my life. It used to be a very sure sign of my impending menstrual cycle.  Then i had a partial hysterectomy and it went away. That was 8 years ago.  My doctor thought it might be related to blood pressure.  I have small vessel disease and since blood thickens when women approach their menstrual cycle it might cause this. (Btw, my mom and sister have this pain also)

Now, 8 years after my hysterectomy it is starting again. I do have one ovary, but not uterus. Im not sure what could cause this. It does seem that it might be related to hormones?

Blood thickening also happens with pregnancy. 

It is very painful.  I cry in my sleep a lot because of it.  Help would be appreciated.