Hm, it seems as though your frog may have become weak and he cannot handle the parasite load in his intestines. Has he been eating regularly? Where does his food come from? You should also be using a multivitamin once a week to get some essential vitamins they need in order to function, not just D3 that comes in some calcium supplements.

I would have a vet ready, just in case you need to take him in soon if things get worse. Make sure his water is 'warm' and dechlorinated like people have mentioned above me. You could try soaking him in some Pedialyte (Electrolyte solution) to bring around unresponsive behavior, i.e. lethargic. Have you noticed him being stressed lately; either caused by handling, noise level, messy enclosure.

Keep him warm in a quiet place, water accessible, and clean until further notice. Don't want any bacterial or fungi buildups from messy enclosures, let him work up his strength. Load him up with a multivitamin the next time you can get him to eat.

I would get some of this on hand until recommended to treat with this: Flagyl (Metronidazole)