What Causes Lower Stomach Pain With History Of Complete Hysterectomy?

I had a complete hysterectomy 18yrs ago and for the past 2yrs I ve been having really low stomach/pelvic pain as well as severe hip n back pain when I lift anything over 15 or so pounds and I have also been having alot of old blood as well as bright red blood, some with small blood clots...Wat could be causing this?