I'm almost sure that he has the cricket stuck in his throat now that you know he was fed a large one.
If you're uncomfortable handling him and trying to remove it, I would look into seeing if you can go into a vets real quick and have them do it. If by off chance it is a respiratory infection instead, you'll still be at the right place for treatment.
He should rub his throat downward if this doesn't stress him in my opinion same effect in rubbing the belly when they are struggling digesting. He should get bee pollen it's good for the digestive track and it has anti inflammatory and antioxidant properties and helps digest it also is a natural antibiotic , it's almost my third powered vitamin lol bee pollen can even prevent wound infection that's why in my opinion great option for silkbacks as more prone to wounds anyway
How large of crickets was he given? I think they were too large for him. Can you get him to
the vet for some help? Be careful though, & try to find a vet who knows how to treat reptiles
so they don't force the mouth open & break his jaw.