Cat breathing heavy and doesnt go to litter... HELP

My cat was diagnosed with upper respitory infection a week or so ago. the vet gave me a medicine to give to him and he was getting well. now he isnt he doesnt seem to cat food only human food, doesnt use the litter very often, and isnt very active anymore and to top it off his breathing has gotten heavyer what do i do. or what is it please help

Heavy breathing is not a good sign your cat is in distress, you need to get your cat to the vet now.