My best advice, change water as soon as possible with proper water conditioner to add more oxygen than it currently has, and if you don't have the funds to buy a new setup, check your local Craigslist or similar online classifieds to find a tank with filter, gravel, aeration, and heat as soon as possible.
Run to your local pet store and find an all in one medication to help. I have mollies and they absolutely love an extra dose of freshwater aquarium salt. It's cheap, it helps with many ailments, adding electrolytes to the water, soothes sores, helps to reduce fungal infection and helps with fin regeneration and fin health in general.
And I think you were possibly describing being lathargic versus nausea? Hope he's not regurgitating.