Bearded dragon losing his appetite?

Bearded Dragons don't drink water from bowls so you have to spray him and he will lick the water off of his lips. You should also feed him crickets as a staple diet (along with fruits and veggies) and use silkworms as a treat every now and then. Do you have sand as his substrate? If you do he could have impaction. The only safe sand to use is untreated play sand. The signs of impaction are him getting skinnier, not eating and not pooping.