He doesn't look well at all, I'm sorry you're dealing with this, but I'm suspecting this is a nutritional deficiency that has to do with inadequate UVB//UVA lighting and improper temperatures, along with a bad diet. He looks quite small/stunted from being a year old, could you please post a photo of his entire enclosure and lights, and a couple of full-body photos of him? It may just be the angle and the fact that the photo is only of his head and neck, but he really looks like he's quite stunted. Do you know how long he is in inches from the tip of his snout to the very end/tip of his tail?
I suspect that the
UVB light that you have been using since you got him is not adequate for a bearded dragon, as this is usually the main cause for these problems. There are actually very few UVB lights sold that are adequate for bearded dragons, even most of the ones that are labeled as being for bearded dragons. If you are using either a compact
UVB bulb (looks like a regular lightbulb) or a coil/spiral
UVB bulb, it is most likely inadequate and he has gotten very little to no UVB/UVA light at all since you got him. This is unfortunately very common, people who buy bearded dragons at pet shops get horrible advice from employees who know nothing about desert reptiles, who have very specific lighting and temperature needs. Without 13-14 hours of adequate strength
UVB light a bearded dragon's body cannot manufacture any of it's own Vitamin D3, and without any Vitamin D3 they cannot absorb or process/use any nutrition that they take in from their food or from their calcium and multivitamin supplements. This causes bone density and vitamin deficiency disease, such as Metabolic Bone Disease (MBD) and Vitamin B1 deficiency. It also stops them from growing and developing correctly and they typically become stunted and have mobility and paralysis issues.
If you can tell us exactly what brand, model/wattage, and type (compact, coil, or tube) of
UVB light you use, whether or not it is obstructed by anything, specifically a mesh lid on his tank (which blocks around 40% of the already too weak
UVB light), and how many inches the
UVB light is away from the main Basking Spot/Platform that he basks on in the Hot Side of his tank? And how old is his
UVB light, have you replaced it in the year since you bought it? This information will tell us if this is the issue.
Also, what wattage and color of basking bulb does he have over his main Basking Spot/Platform in the Hot Side of his tank? And what type of thermometer due you use to measure his temperature zones inside his tank (stick-on, Digital with a Probe, or a Temperature Gun)? Do you know what the temperatures are for his Basking Spot Surface Temp (should be between 100-105 degrees), his Hot Side Ambient (air) Temp (between 88-93 degrees), and his Cool Side Ambient (air) Temp (between 75-80 degrees)? Do you use any other lights besides a
UVB light and a Basking bulb? Also, how many hours do you leave both his
UVB light and his basking light on every day?
I'm also assuming his diet is not good, mealworms are not a live insect that should be fed to bearded dragons as a daily staple insect, they are mostly all very hard chitlin shell, which dragons cannot properly digest and may have also caused a bowel impaction, this is very common. The rest of mealworms is mostly fat, so this is also contributing to his stunted growth and sickness for sure. Bearded Dragons continue to grow up until they are 2 years old, but 80%+ of their growth is done during their first year of life. This is why not many babies or juveniles eat many greens or veggies, because they don't need them and don't have to. If a baby or juvenile dragon under a year old does eat greens and veggies, it should only be considered a bonus and not a real part of his daily diet. They need tons and tons of live, healthy staple insects every single day up until they are at least a year old. They should be fed these live insects in at least 2 daily feeding sessions every single day, 3 feeding sessions daily is better up until at least 8 months. Each feeding session should last between 10-15 minutes and during that time period they should be allowed to eat as many live, healthy, staple insects as they want to. These insects include gut-loaded crickets, Dubias and other species of roaches, Silkworms, or Phoenix Worms/BSFL/Caciworms/Nutrigrubs/Reptiworms (all the same thing just different brands).
For example, I currently have a 6 month old boy who eats BSFL/Phoenix Worms as his primary daily live insect. I gut-load his BSFL every day with the same healthy greens that I offer him every day, which include collard greens, turnip greens, mustard greens, dandelion greens, escarole, endive, bok chok, swiss chard, and arugula (no kale and no spinach, bad for dragon because they bind any calcium they eat and prevent calcium absorption). I turn his UVB and his bright white basking light on first thing in the morning and let them on for at least 1-2 hours before feeding him anything so he will be better able to digest and absorb his nutrition. Then I give him his first 10-15 minute live insect feeding session of the day, where he typically eats between 15-20 large BSFL. Then I put a salad of fresh, healthy greens in his enclosure (though he doesn't eat much at all) that I leave in until I turn his lights off for bed. He gets his second live insect feeding session around 1 in the afternoon usually, sometimes later, where he usually eats the same, between 15-20 large BSFL. Then he gets his third and final live insect feeding of the day around 7 at night (you must allow him at least 1-2 hours under his lights after he eats his final meal of the day before you shut them off for bedtime). During this 10-15 minute feeding session he usually only eats around 10 large BSFL. So at 6 months old he usually eats between 40-50 live, large Phoenix worms every single day. I dust one feeding of his worms per day in calcium powder 5 days a week, and one feeding of his worms per day in a reptile multivitamin powder 3 days a week. I order their live insects online in bulk, as most owners do (I have 3 dragons), you save a fortune and this makes healthy feeders available as most pet shops only carry crickets, no roaches, silkworms, or BSFL. I give them live insects that are considered "treat" insects 2-3 days a week, and they include wax worms, butterworms, and hornworms (and superworms for my year old girl who is 19" long and can digest them; never feed a dragon any size of superworms until they are at least 14"-16" long, they cannot digest them otherwise). Mealworms in my opinion should not be fed to dragons at all because there is no nutritional benefit to them at all, only bad stuff. They don't contain much protein, hardly any fluid for
hydration, most just hard shell and fat. Some people choose to feed their dragons mealworms as occasional treats, which is fine, but we're talking a few a week.
I'm so sorry your son's dragon is not well, but we will do everything we can to help you get him on the right track once we have more info on what's going on...