Meal worms should only be fed as an occasional treat. It sounds like you've been feeding too many meal worms and he has become impacted. Frogs cannot digest the exoskeleton on a meal worm as well as they can on crickets. Too many meal worms can really bind them up. Try doing a shallow soak in warm water with a drop or two of Honey. I highly recommend doing this nightly until you see poop. When is the last time he pooped? You may also want to use a calcium supplement in the soak so he doesn't develop a deficiency. This is the best advice I can give you. Hopefully someone with more experience in treating ailments can give you more advice. Good luck.