Thanks for writing in,
Sorry to hear your little guy is having a tough time breathing. If he is in respiratory distress then I would suggest getting him to a vet ASAP. My concern is that he may have a heart condition and now is developing fluid in his lungs or he could have a primary lung condition that is causing fluid build up. Until you can get him to a vet ensure he is in a cool environment and keep him very calm. I hope your guy will be ok, please let me know if you have any other questions.
Dog Veterinarian
Veterinarian, Dog/Cat Veterinarian