I have suffered over 20 years from IBS-D, half a dozen GI doctor stealing my money because they can't Dx a hole in their own rear end. After spending the last year researching my condition I have diagnosis myself with celiac disease. It's turns out to be gluten. I have been on a gluten free diet for two month and feeling %80 better so far. I notice a huge improvment just after two weeks. Maybe your doctors suck as bad as mine.