[anonymously]

You mentioned you have a health care insurance plan for your dog. I would ask his veterinarian for a referral to a board-certified Veterinary Internal Medicine Specialist, as you have been going back and forth to the vet for years (as described in your previous post) and the dog has not responded to the treatment prescribed by them.

In fact, if it was my dog I would insist upon it, I would speak to someone in a higher position if I had to.
When you have a serious issue that has not been resolved or shown adequate improvement by the regular veterinarian in a reasonable amount of time, I recommend seeing a specialist.

PS: Your vet can fax his records to the specialist…or you could obtain copies, they might be available online, a lot of vets have portals now, like with our medical records.