IT could be a couple of things, i agree with the above reply that it could be an impaction and its important to have high basking temps, but i have to add that a ten gallon tank is WAY too small to have a beardie in if you are going to have proper basking temps (100-110degrees) please move your beardie into at least a 20gallon long before you up these temps or you will cook the little guy! Warm water soaks work well.
What kind of supplements and lighting have you been using? Not having the right kind of lighting (UVB) or not having enough calcium supplementation can lead to MBD, which in babies is frequently shown by paralysis of the back legs. How long have you had him? Even if you are doing every thing right he may have had inadequate care before he came to you. I would take him to the vet, along with a fecal sample if you have one. I worked with a baby beardie one time (very small, under 3inches) who came to me paralysized in the back legs, very weak and lethargic even though i had had him under the correct lighting and had been supplementing. It took a long time with liquid calicum drops (prescribed by the vet) and force feedings and tease feedings before the little guy was up to speed again.
please don't delay, try the home remedies for impaction buy if he doesn't poop soon, take him to the vet immediately. and please please please do not up his temps until you have him in a larger tank.
good luck with everything!
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