Like Grif asked, when was the last time he pooped? My opinion is that meal worms and crickets are a lot of hard crunchy feeders and I would be concerned about impaction. If you haven't seen any feces, I agree you need to let him soak in warm water. When I don't see my Fowler's toad poop I use warm water, he'll soak for hours then ta-daa, all better. I would mix his diet up with worms and roaches, something a little softer yet still very nutritious. Also if he wants to hibernate let him. My female has been underground for 3.5 weeks now, my male goes down for a few days or 2 weeks then comes back up. I've read several places where hibernation extends their life span and I'm all for that.