Hey bunny. They should definitely check you for celiac disease (blood work and biopsies) before giving you a diagnosis of IBS. They should also do several ova/parasite exams and probably a stool culture to rule out the possibility of bacterial infections. Have they ever done this stuff?
I have foamy diarrhea sometimes too. Actually a few times today I've had it. Then again, I'm told it's not IBS. But they haven't told me what it IS yet.