Have you been checked out by a gynocologist?
I did have both an upper and lower GI scope. They took samples from my small intestine, but the biopsies came back normal. I have a gynecologist working with me right now. I don't smoke and haven't drank any alcohol in months. The pain is pretty well scattered throughout my abdominal region. But I have noticed that the sharper stabbing pain is located beneath my rib cage on both my left and right side. When the pain first occured it did build up over a 7 day period but when it came back a month later it built up and then remained constant. So it's been there now for about a month. My stool has alternated between black and green, and I was 2 wks late on my menstrual cycle. The only thing that I have noticed that makes it worse is sitting for long lengths of period and physical activity. I am planning on speaking to my doctor about possible dietary causes like an allery to gluton or too much msg. It is strange though when i sit for too long, it feels like one of my organs on the mid left of my abdominal region is trying to push its way out of my skin.
Get checked for Celiac disease.
The ER really isn't the place to go when you have something that can't be quickly diagnosed and treated. Their job is to assess the illness or injury, get the patient stable, and then pass the case on to the appropriate doctor for further treatment and followup. I suggest that you visit the hospital and get copies of all written reports for lab work, CT scans and your ultrasound and any other tests, and find a gastroenterologist.
The next step to investigate your pain will probably include an endoscopy. The gastro doc can look at your esophogus, stomach and upper part of the small intestine using a flexible tube with lights and a small camera. It even has tiny instruments that can take biopsies and other small surgical jobs at the same time. The procedure is done under light anesthesia so you shouldn't be aware that anything is going on at all.
Is the pain all over your abdomen or is it in any particular quadrant like light upper right or left, lower right or left? Right in the middle between your ribs? Does anything make it better or worse? Do any foods make it better or worse? Do you drink alcohol or smoke? Any trouble with bowel movements or urinating? Any changes in menstrual cycles?
One thing that caught my attention is that you mention it lasts for 7 days and appeared again a month later. That may mean it's something hormonally driven or gynecological (maybe about the time you ovulate?), so a visit to your gynecologist wouldn't hurt. Endometriosis can make a real mess of your abdomen so that's something to ask your gyno about.
There are so many things that could be going on and the ER has done about all they can for you. It's time to approach this from a clinic standpoint. Depending on your insurance, you may need to start with your primary care physician to get the ball rolling with referrals to appropriate specialists like a gastroenterologist. I know it's awful to be in pain and want it to go away as soon as possible, but with the cadillac workup you've had at the ER already, it appears you'll have to be patient and work through the system to get answers.