You mention food allergy tests. Can you be more specific? Because if you have been tested for GI was it negative and then you tried being GF? Well I would try gluten free again and also doing tests. Definitely get all the food allergy tests, especially fructose. It is a definite suspicion to your continued symptoms. Otherwise my very first thought was stool test but you said you have done that. I know I would suspect something along that line with such continuous D. I am firmly convinced that Heather's diet works wonders for IBS-D folks that do not have some other condition.
-------------------- IBS-A for 20 years with terrible bloating and gas. On the diet since April 2004. Remember this from Heather's information pages:
"You absolutely must eat insoluble fiber foods, and as much as safely possible, but within the IBS dietary guidelines. Treat insoluble fiber foods with suitable caution, and you'll be able to enjoy a wide variety of them, in very healthy quantities, without problem." Please eat IF foods!