Hi Judith, I'm Linda, a vet with 10 years of clinical experience.
I'm sorry to hear about this ongoing diarrhoea.
This sort of diarrhoea can have a wide range of causes including:
- A food allergy or sensitivity
- A bacterial infection
You don't mention which tests were run but I'd hope they analysed his stool and scanned his abdomen. A blood test is also useful, especially if we run an intestinal panel which can check levels of cobalamin and folate and well as Tli.
As well as a fiber supplement, I'd start a probiotic and a hypoallergenic hydrolysed diet. When on this diet, he should have no other food or treats.
I'd also ensure he is up to date with a broad acting wormer such as Fenbendazole.