Fon: I think they need to run the stool tests again and perhaps at a better lab. Maybe even go to a different GI specialist or teaching hospital if you can!!! This is NOT your run of the mill IBS-D. I had similar issues and actually needed ANOTHER antibiotic called Tetracycline to make me better. I am just worred that you may have c-dif and it was missed. If that is the case, you may need to be in the hospital on IV antibiotics depending on the strain. On the other hand, if the sinus infection antibiotic caused too much die-off of your good bacteria, it is possible that bad bacteria overgrew. Your case demands a better doctor and better institution. A loss of 40 pounds is very scary. That is what happened to me and by the time they finally figured it out, or should I say, were ready to try anything, I had dropped below a size 2. I am five foot nine and normally wear a 10 (female). My prayers to you that they find something out very soon. Any doctor that thinks weight loss is common to IBS is wrong. It also can take up to FIVE consecutive stool samples for a proper analysis. I know you feel horrible but be your own best advocate and demand another and better round of stool tests! That is just my layperson's opinion.