They need air to breathe, so he is probably struggling up for that. Also possible that the systemic fungus is causing pain/seizures/etc.
You really need to take some of the suggested steps very quickly, or he will die. A big shallow plastic food container from the grocery store is really low cost, a .99 thermometer, a heater, some aquarium salt, some Jungle Fungus Clear.
I totally hear you about it being a lot more than you expected, or can afford. If you really can't, you can't. Hopefully, you can find these things in time.