Go back to the vet. Find a vet that you trust and work closely with him. You may need the expertise of an Veterinary Internal Medicine Specialist.
This is not a do it yourself, the right dog food will not fix this. Prescription dog food in conjunction with other recommendations by the treating vet may help.
The dog may need some additional testing for diagnostic purposes, something else may be wrong.
The internet is not the place to go for medical advice, you could possibly do more harm by listening and taking advice given by people that mean well….but they are not health care professionals nor have they examined your dog.
Depending on how severe the dog’s symptoms are, I may consider taking him to the emergency vet , today.
