Can we get the specs for your set-up?
Tank size, lighting, temps, substrate, what you have been feeding him, lighting schedule(when the lights are timed to go on/off),and do you dust your crickets?
Beardies should eat lots of crickets as babies. My Marvin when he was smaller would eat 30-35 pinhead crickets twice a day. They do ALOT of growing their first months.
feed him crickets but lettice carrets and peas
Please do not feed him this. If you want to give him any nutritional value feed him this:
Dandelion greens, Collard greens, Mustard greens, Bok choy, Kale, Turnip greens, Escarole and Chicory
Anything that says "Lettuce" in the name is mostly water...so no good.
Do not feed any worms till your beardie is at least 5-6 months old, and then only as a treat. Crickets are their main diet till then, and then you can think about switching to Dubia Roaches.
When he scratches at the cage, is it the same spot, or is it like he is looking around? And do not get him a leash at this age...he is way too small.