Hmmm...you might want to have him checked for heartworm, then, sbainbr. There's a monthly preventive for it, but it isn't controlled by regular dewormings which just deal with intestinal parasites. One of the symptoms of heartworm infection is labored breathing... The test is fairly simple--a blood test. There's even a snap test for it these days which gives you results immediately.
Beau and Oscar are dolls!
And so good with the antlers!
They must love Christmas!