I know you've been tested for Celiac...but you sound just like me and I might very well have it! Which fiber supplement do you take? I might try eliminating gluten from your diet for several weeks just to be sure. It can't hurt! You'll feel SO MUCH BETTER if it's the culprit! Eating gluten free is not just about bread and eliminating pasta though--one speck of gluten is a problem. I can help you with the diet if you decide to try it...so let me know what you decide to do. I know it's not fun--but it's worth it to feel better! Either way, I'm here...and I hope you feel better soon! Take care, feel good!