There's nothing a vet is going to be able to do for a pygmy chameleon, unfortunately, they're so small!
I'm super sorry to hear this. Unfortunately pygmies don't live very long to begin with and most come in of unknown age, so it could be his time. Unless you think it's something else, and we can try to go over your set up and husbandry and see if anything jumps out at us.
Again, I'm really sorry!