sorry for your doggie. I know this will be hard for you at first, but I think the best thing you can do right now is to stop feeding your dog industrial food and switch to a raw diet. Depending on where you live, some petstores even sell premade raw food for pets, which is kept frozen.
Or if you have the time, try feeding him only raw organic meat for a couple of weeks and see if it bgets better
i also recommend flax seed oil
Trythis website and use the search feature for info