First, no more meal worms at least until he gets bigger. I've always heard that their exoskeletion is very hard for BD's to digest and can cause impaction. Second soak him in warm water and see if maybe he poops, perhaps he's a little constipated and thus won't eat. If not check check check your temps. If he's not properly heated up he will not eat. Trust me 3 crickets is far too little.