Bearded Dragon Acting Lethargic?

Since your husbandry seems to be in order, I also recommend you seek vet istance, especially with one so young. I recommend taking a fresh fecal sample to the vet and getting it tested for intestinal parasites. You can try to call around and see if you can find a vet that will simply charge you for the fecal testing itself without bringing the bearded into the office. You can also ask vet offices if they have a "payment plan" available; allowing you to pay off the bill in installments. The bottom line is that the vet is the best course of action in this situation.