Pelvic pain on right side

Here I go again. I have had severe pelvic pain twice in 2 yrs. It's so bad that it can be dibilitating and I go to the ER. The dr's run tests ultrasounds,ct scans and nothing!? All test come back normal but, yet I still have severe pain. I had an endometrial ablation 2 yrs ago to stop the heavy periods I was expericing. It has helped except for twice when I do get the extreme pain. I start to bleed but, not like before and end up in the hospital. I am confused and I need someone to let me know If they are going through the same thing and did your dr find something that my dr's aren't? Please help!