Veterinary questions? Ask a Vet for Answers ASAP
I am sorry to hear you are having problems with your cat. Yes this is very concerning. Obviously when warm cats will pant but only when they are very hot. Usually this should resolve within a few minutes back into normal temperatures. A few hours of fast breathing and panting is quite concerning. I would definitely advise having him checked by a vet. It could be related to his previous mycoplasma infection. There are many reasons why cats could have breathing difficulties including heat stroke, infection in the chest, fluid accumulation in the chest etc. I would advise calling your emergency vet ASAP. I hope he feels better soon.