Your frog is suffering from malnutrition, seems to be acting spasmodic resulting from this. You need to force feed him or her a frozen-thawed mouse or a few night crawlers. Buy the liquid calcium and liquid vitamins with a syringe that comes with it and inject it into the mouse. If you are going to do night crawlers, supplement those with a 1:1 ratio of calcium with d3 and multivitamin to get your frogs nutrients back in him or her. This may cause digestive uptake, but with a proper ratio of 1:1, it shouldn't affect your frog's metabolism. Reason being is he needs both quickly, multivitamin and calcium with d3.

Procedure for force feeding:
1. Take a spoon, butter knife, or credit card.
2. Gently lower the bottom lip of the frog while having your other hand ready with the tongs.
3. Once frog opens mouth, insert real quick and let him or her do the rest of the work.

Hope he or she pulls through - 3 weeks without food is not good. Update us please.