Thanks for using JustAnswer.com, I'm Dr. Dan and I'll try to help you.
Is your beardie interested in the insects (does he track them or try to strike) or is he just ignoring them?
What is the temperature of his environment (basking and cool)
What is the humidity level of his enclosure?
When was his last shed? Is he currently shedding?
Is he active or does he just tend to hang out in one place through the day?
Is he your only bearded dragon? If not is he alone in the cage or does he have a partner?
With this description I am concerned about a couple of things.
Since he is a baby parasitism is always a possibility. Young animals can sometimes loose the battle when it comes to feeding their parasites and when this happens the dragons themselves stop eating. This is fairly easily diagnosed with a fecal sample at the vets. The other two possibilities are a minor intestinal infection causing nausea and not eating, if this is the case a round of simple antibiotics will make a dramatic difference. Because you are describing wasting or weight loss the third possibility of adenovirus is possible. Adenovirus is passed from beardie to beardie usually via the mother. The virus can lie dormant for a long time or get to work early in life. The hallmark symptom of adenovirus is a healthy lizard that won't eat and wastes away. This can be tested for by swabbing his mouth or rear end with an experienced vet. We hope it is not adenovirus as there is no cure. I would consider a vet appointment for a fecal test, adenovirus test, and a round of antibiotics. It sounds like the environment is pretty good as long as he has not been feeding on sand or bark bedding. If he was then impaction of the bedding in his intestinal tract is also possible and is diagnosable by xray and curable through surgery.
I hope this helps, if you have more questions, please ask.