What Causes Lower Abdominal Pain And Diarrhea?

I am a 22 year old female. I have had a very sensitive GI system my whole life and have had many problems from heartburn, diarrhea, nausea, cramps, constipation, the list goes on. The past 2 months I ve been having a crippling pain in my lower back/lower stomach/groin area. My DR thought is may be a female related issue and ordered a internal and external sonogram. A very, very small (about 3/4 of a CM in size) fibroid was found but my gyno does not this that is the reason for the pain...I do not think it is either because the pain has begun to happen most often before I have a bowl movement, during one, or after one. Sometimes it happens during intercourse, sometimes during urination, and sometimes after eating. This pain is not a burning or just a little cramp, this pain is a crippling pain that makes me double over in pain, gripping my stomach. I was given a short term anti-inflammatory (Ketorlac) and it does nothing for me.