I'm sorry you're beardie is so sick, but this is completely due to inadequate UVB lighting. It doesn't matter how much Calcium or Multivitamins you give him, or how healthy his diet is, without a very strong, adequate UVB tube, in this case as Tracie already told you, he absolutely needs a T5 strength UVB tube, the 22" Reptisun 10.0 T5HO UVb tube ($23 on Amazon.com) and then a 24" T5-rated tube fixture (cheapest that includes a metal reflector inside it is the Sunblaster brand 24" T5 tube fixture, $26 on Amazon.com). You can have the T5 UVB tube on top of a mesh lid, but it still must be within 11" of his basking spot, and replaced once a year at the longest. Both this T5 UVb tube and a bright-white colored Basking Bulb (that is the adequate wattage to keep all 3 of the tank temperature zones within the correct ranges) need to both be positioned over the Hot Side of the tank and both right alongside each other, and then you need to move his Basking Platform directly underneath both lights so that he gets both while he's basking. They both must be on for at least 13-14 every single day.
You need to get rid of the red night light, he needs NO nighttime heat source at all unless the temperature inside his tank drips below 65 degrees, which it most likely does not, your house would have to be 60 degrees or below at night for his tank to drop below 65 degrees. The Australian Desert where they are from, at night is #1) Pitch-Black with no light at all, and #2) Very cool, even cold...As a result Bearded Dragons sleep soundly and comfortably only when it is Pitch-Black inside their tank, and considerably cooler than it is in the daytime. Even if you wanted to keep his tank a bit warmer than normal at nighttime since he's very sick, you still cannot use a light of any kind, least of all a colored light that is red, blue, green, yellow, purple, black, "moonlight", etc. If you wanted to add any type of nighttime heat source, it should only be a very low wattage (like 5-10 watts) Ceramic Heat Emitter (CHE), which screws into the lamp you already have, but it only emits heat and no light. For now, please completely turn off that red light.
Bearded Dragons see in full color, and as such you cannot use any colored lights for them during the day (most importantly) or at night. That red light is confusing his night and day periods, masking his food, and hurting his eyes. And again, he'll be much more comfortable at night if it's cooler.
I hope his daytime Basking Bulb is a bright-white Basking Bulb or Halogen Indoor Flood Bulb, you're trying to replicate natural sunlight over his Basking Spot/Platform, and you do this by putting a very strong, adequate wavelength, long UVb tube right alongside a single Bright-White colored Basking Bulb, both over the Hot Side of the tank and directly over his Basking Spot. Most of us do not buy expensive Reptile Specialty Basking Bulb, we simply use regular Halogen Indoor Flood Bulbs, like you buy at Lowes, Home Depot, or Tractor Supply (they have 2-packs of the par38 Halogen Indoor Flood Bulbs for $10)...I don't know the size of your tank or what your 3 temperature zones measure, but for reference, usually a 40 Gallon Breeder tank requires a 100 watt or 125 watt at most, bright-white colored Halogen Indoor Flood Bulb over the Hot Side of the tank to reach the proper temperature zones.
The main issue here is that you need to get the T5 strength, long UVb tube immediately. Without 13-14 hours a day of strong, adequate
UVb light, Desert Reptiles (especially Bearded Dragons) stop manufacturing any Vitamin D3 at all, and this in-turn stops them from being able to absorb any of the nutrition (calories, protein, fat, carbs, etc.), vitamins, or minerals (calcium, etc.) that you feed them in either their live insects, their fresh greens/veggies, or their supplements, such as calcium or multivitamin powder or liquid. Instead, they just excrete everything, and this creates severe malnutrition and several different nutritional deficiency diseases, including MBD and Vitamin B1 (Thiamine) Deficiency. Their bone density weakens, they totally lose their appetites, they become extremely lethargic, their muscles start to waste away, and the final stage ends with broken bones, paralysis, and death. Your poor little guy is definitely suffering from severe Calcium deficiency, malnutrition, MBD, and probably kidney and liver disease/failure....he needs the T5 strength UVB tube immediately, without it on for at least 13-14 hours a day, he's not going to get any better...
It's a shame, but 95% or more of the UVB lights that are sold are totally inadequate for Desert Reptiles, and this includes most of the UVb lights that are labeled as being meant for Bearded Dragons. Pretty much ALL compact (regular lightbulb shape) and coil (same as a compact but in a spiral/coil shape) UVB lights are far too weak to be used for a Bearded Dragon, they are pretty much all half the UVB wattage/strength that a Bearded Dragon needs (13 watts or less in most cases)...And on top of the UVB lights being inadequate and far too weak, most people have them on top of a mesh lid to the tank, which blocks an additional 40% of the
UVB light from the already too weak
UVb light, so their dragons have basically gotten ZERO
UVB light...they also must be replaced once every 6 months at the most, as they have a very, very fast UVB decay rate, so even though they are burnt out and they still turn on, they no longer emit any
UVB light after 6 months old, some of them it's closer to 3 months old.
Also, all compact and coil UVB bulbs and the much weaker T8 UVB tubes must be within at least 6" or closer to the dragon's basking spot/platform, in addition to having to be unobstructed by anything like a mesh lid or a clear plastic cover, and most people don't know this, plus putting those UVB bulbs that close to your dragon can cause eye damage and neurological damage, so this is why Dragon owners must buy a very strong, long UVB tube that is of the T5 strength (24 watt minimum). (your guy absolutely must have a T5 strength UVB tube and fixture, a T8 strength UVB tube isn't going to help him much at all, and they tend to actually be more expensive or the same price as the 22" Reptisun 10.0 T5HO UVB tube and a 24" T5-rated tube fixture cost on Amazon.com).
There is a post in the "General Discussion" forum here titled something like "Amazon.com Links for the 22" Reptisun 10.0 T5HO and 24" T5-Rated Fixture" that contains the links for both the 22" UVB tube he needs, and the 24" T5-rated tube fixture for this UVB tube on Amazon. Best prices I've found anywhere, I just ordered 3 tube replacements for my guys 2 months ago...