How can I get my dogs well & find out what is wrong with them?

I have 3 Labs. I don't know exactly how to describe what is wrong, but I will try. They have a terrible crouping gagging gasping dry sounding cough. At times they sound like a pig oinking or a goose honking. It's as if something is caught in their throats. They also seem to have trouble breathing in & out of their noses off & on, making strange gasping noises through them as well. I am so worried. I've taken them to a couple different vets, but they don't cough while there, of course. They check out fine otherwise. I was told it's kennel cough. I've tried steroids, anti-inflamatory drugs, & antibiotics now. Vet also had me buy OTC cough medicine for them. Nothing is helping. It has been 11 days now. What is wrong & what can I do to help my poor babies (dogs)? Any suggestions would be appreciated. Thank you.