I just called the vet and talked to the secretary and she said that if it's a dry hack then it's a sign of heart worm, if it's just like he can't breath, which his is, then it's called a reverse sneeze and it's very common in dogs. Heartworm can't be gotten until mosquitoes are out and here they don't start coming out until April so between April 15-June 1st I should bring him in for testing and a prevention.