My guess is that he's severely impacted from inadequate lighting and temperatures, plus the mealworms and freeze-dried insects. You need to completely stop feeding him any mealworms or freeze-dried insects at all from this point forward. Mealworms have very little nutritional value at all, they are full of fat, and most importantly they are mostly nothing but chitlin shell that is way too hard for bearded dragons to digest, and they often cause lethal impaction. Freeze-dried insects are about the worst thing you can feed a beardie, in fact they are the only thing worse than the mealworms, especially for a baby or juvenile. They have zero nutritional value, no moisture at all, cannot be gut-loaded obviously, and are literally like feeding your beardie cardboard or wood that cannot be digested. The hard, indigestible food combined with bad lighting and improper temperatures will definitely cause a bad impaction, along with stunted growth, nutritional deficiencies and diseases, such as MBD and Vitamin B1 (Thiamine) deficiency, and eventually paralysis. You need to pick a high-quality, only live feeder that you can gut-load with fresh greens and veggies, like live crickets, live dubia roaches, live Phoenix Worms, or live Silkworms. Obviously crickets and dubia roaches are easiest to find and cheapest to buy, and if bought online in bulk you save a fortune. Either way, no more freeze-dried insects or mealworms at all or this will keep happening, along with far worse and permanent disabilities and possibly death.
Get some prune baby food at the grocery store, along with a can of raw pumpkin from the canned veggie aisle, and a bottle of unflavored Pedialyte (store brand is fine, all can be found at Walmart cheaply). Empty a jar or container of the prune baby food into a microwave-safe container and then add 2-3 tablespoons of the raw canned pumpkin, then a pinch of his Calcium powder WITH VITAMIN D3 and a pinch of his multivitamin powder. Then add a little of the unflavored Pedialyte to thin it out a bit so it can be delivered in an oral syringe or eyedropper. Mix it up very well, then microwave it for a minute. Mix it very, very well again, and test it on your wrist like you do a baby bottle. You want it warm, but not hot. Drip it on his snout, let him lick it off, then drip again, lick it off, drip again, etc. Let him eat as much of it as he wants, and do this 2-3 times today, then tomorrow morning. Then put him under his lights tomorrow morning after he eats the slurry again for an hour or two, then give him a warmer than normal
bath, along with gentle tummy rubs down his right side. He should poop.