What Causes Painful Periods And Fluid In Abdomen?

i am a 24 year old female. I have very painful period and pain during intercourse. Also all times during the month i will have pain in my sides, and under my ribs. I have been told that I may have PID, ovarian cysts and gall bladder problems. all my test have came back negative. The doctors have found fluid in my abdomen twice but no cysts. I am currently taken naproxin for the pain but it doesnt help at all. What else could it be?