In January I got a sinus infection, took an antibiotic, and after the course started getting massive bloating/gassy pain nearly everytime I ate. Naturally, you go to the Breads, Rice, Applesauce, Toast diet, didn't work. Got a CT scan done with Barium, C-Diff Fecal sample done, blood in stool test,Celiac Bloodwork, Intestinal permability test, ALCAT Allergy test, another sample test. Everything came back negative, except for the Allergy testing came back allergic to the Nightshades and Onions. I've even cut out all Gluten for the past 3 months. The pain seems to come and go with massive bloating/cramping. An episode will last maybe 10 minutes, then it will go away with either BM or on its own. More often than not, this occurs in the evening after dinner has settled for a few hours or instantaneously with dinner. Breakfast and Lunch are usually ok, just grumbling. I would consider myself regular with at least 1-2 BMS daily(always normal).

What more could this be?

have you been checked for crohns disease or ulcerative colitis?

I have not because the doctor(s) have told me that without any diarhea, no blood in stool(not even microscopic), and everything on the Barium CT and Bloodwork showing nothing wrong that the Colonoscopy is the last thing to run. Obviously those are the 2 diagnosis that would be confirmed from a colonoscopy, but most GI's are so quick to diagnose this without looking for food allergies, etc.

Rogan, are you taking probiotics with each meal? You probably know that antibiotics can mess with your stomach, etc.. maybe the flora in your intestines needs a kick-start, to restore itself to the way it's supposed to be? Not suggesting this is the only issue- I'm in a similar boat myself. (I'm going to have a scope on the 15th).

If the dr's can't seem to find anything wrong with you, for now you could buy yourself some good acidophillus/probiotics (something with at least 1 billion live cells per tablet or whatever), and take a couple with each meal. See if that at least helps somewhat.