Sick African Clawed Frog!!!

Hello!

I have an African Clawed Frog, Hippie, who I have had no problems with! He's been as happy as can be until recently. One morning I went to go check on him and he wasn't his normal self. Usually he will swim to the top very active and trying to get my fingers and get some tummy rubs. But now he's not so active and sits stationary. He just sits at the top and doesn't really swim around unless he needs to. All his limbs are working when he does swim. The other thing is he isn't eating. Not bloodworms, krill, frog pellets, nothing. When I changed his water yesterday he opened his mouth and it almost looked like there's a piece of krill stuck in it. But I mean I never know what his mouth looks like on the inside. I don't know if I should try opening it up or what cause he's still such a small thing. I put a light in my room today for him thinking maybe it's because he needs a light cycle but where ever I put the light he goes to that area of the aquarium and just sits by it.

A little about the tank:
-10 gallons
-filtered
-kept at room temp but sometimes gets cold (when changing his water it was cold!)
-I know I'm going to get yelled at for this but I don't test his water because I use spring water to change him with.

I'm not sure if it's cause his water is cold and he gets dormant and if I should heat his water up, not sure if he can't poop or something is obstructing his mouth. I've tried googling everything but can't seem to find an answer!

Anything will help Thank you!

What's the timeline? You changed the water yesterday (partial or full change)? When did he stop eating? How cold is "cold"?

I would recommend a larger tank for an ACF. (He's not the dwarf clawed frog, right?)

Wednesday is when he wasn't the same (active wise), and Thursday he wasn't eating. It was time for a full change on Friday, so I changed it thinking it might make him feel better. I put my finger in his water about an hour ago and it felt room temperature. My roommate said that while I was changing his water, that it was cold. But i feel like maybe it was because I was in the middle of changing it. So normally the room he is in is between 75-80 depending upon how warm the room gets during the day. In all honesty I have no clue what type of clawed frog he is. I just know he is a clawed frog because of his little toenails. He is about the size of a half dollar right now and he is only about 4 months old.

New Update: It now looks like his skin is like peeling off of him. Like a cloudiness is coming off of him.

At that size, a 10-gallon is fine. Abnormal shedding is a bad sign, but it could indicate a lot of different things. It can indicate bad water, but it can also be a general sign of ill health.

Do you always use the same type/brand of spring water? Any uneaten food in the tank? What kind of substrate (gravel, pebbles?)

Room temp should be perfect, I wouldn't worry about that. 75-80 is a little on the warm side.

Yes, I've used the same brand since I've got him and I've used the same brand for all of my fish. No uneaten food, I take it out after 5 mins of him not eating it. And there is gravel in his tank. Would it be easier if I upload a picture of him?