Has there been any changes in diet, behavior, lighting, or temps? How often is he basking and what are his basking temps? How old is his
UVB light? All of these questions will help eliminate other possibilities.
It's always best to have a fecal preformed just be safe. I'm almost positive The individuals that run this site perform fecals and could provide you with more info. Though I would like for someone else to comment on that since I'm newer to this forum.
You can also check out beardeddragon.co
Or look up "
black beard dragons" (by doctor dragon) on facebook and shoot them a message. For $12 you can mail them a sample and she will call you and tell you what your dragons has and tell you what and how much medication he needs. I've heard great things about them.