In the last two weeks my dog has suddenly started drooling uncontrollably. He is also starting to hack/cough a bit. Today he is refusing to go poop. We've taken him to the vet, and blood work came back OK, they cleaned his teeth, and he is STILL having the problem of the drool. This is such a sudden change we can't help but think something is wrong with him. We also can't afford to keep going back to the vet. Can anyone help me?