Black Morphs
Truth is we haven’t seen any black morphs being offered as of now. Scientifically they would be hypermelanistic, and these dragons would have an excessive amount of dark pigments leading to a very dark appearance overall. We hope to one day see such a dragon be bred with regularity, but to start there would have to be a few dark dragons brought together to work with. For those of who you say, “But wait, I’ve seen pictures of all black adult bearded dragons before!” to which we would reply, “Correct you are, but with almost certain positivity we can assure you those images were of wild bearded dragons from Australia, and more specifically Eastern Bearded Dragons, a very close cousin of the central bearded dragons, which is what virtually all bearded dragons in domestication are.” With that said, even if it wasn’t a biological faux pas to cross breed 2 different dragon genotypes, it is illegal to export any bearded dragon from Australia now, making sourcing such a dragon nearly impossible. With no known truly dark dragons gene pools in domestic breeding existence, this dragon becoming a regularly available morph may be dependent on a bit of luck.
http://beardeddragonsource.com/info-center/about-breed-types/
Now this is not to say your dragon is a black morph, it may be totally stressed, or even ill. A vet would be better to tell you whats going on with him. But this is what I found on the black morph