Sounds like Zoe two months ago. We called the vet and they said it sounded exactly like KC, but that it should resolve on its own. It didn't, and weeks later we ended up still going to the vet. Turned out she had a bacterial strain of an upper resp. infection.
I'd say just go to the vet, don't want him to develop a secondary infection (pneumonia). Good luck!
Zoe 05/24/11 Boxer, floppy and natural and Macy Rae 10/26/06 English Bulldog
Do not follow, as I may not lead. Do not lead, as I may not follow. Walk beside me and be my companion.