Did you give him a parasite treatment? I think theres definitely a blockage of some sort! Try adding a disolving de wormer into the water (make sure to follow dosage instructions) How often are you doing water changes? I would make sure his water stays crystal clean, keep adding the epsom salt as well.
I once had a betta with a bad bacterial infection in his head, it was all swollen, poor thing. I was told to put a warm damp wash cloth over the top to keep it extra humid in the tank, you can also put plastic wrap over the top of the tank to achieve the same effect. It really helped to bring the swelling down. I know hes bloated and not swollen but it still might help, and it won't hurt!