update!!!
Thank goodness the news isn't bad..
however I was hoping for an actual diagnoses and really didn't get one, right now we are ruling things out. He hasn't coughed once since he has been at the vets, which I guess is good news. They ran a heart worm test that came back negative. She said that to her, he seems out of breath at times but thinks that his weight is causing that. She said his lungs were clear. They ran a blood panel to check his white blood count and his thyroid level (shelties are prone to this) and it came back fatty, this has happened in the past we retested him a week later after a 12 hour fast and it came back normal. They are putting him on a restricted/prescription food diet and they are going to retest him again in a week. She said that he isn't "old" more "middle aged" but is aging faster than he should.
She wanted to start weaning him off the pheno but because he just had a seizure a month and half ago while on the pheno she wont. The pheno is contributing to his weight increase. She also mentioned that it may be an allergy, but its more than likely his thyroid but until she can redo the blood work we wont no for sure.
I feel better now, knowing that he will be ok. I know that I probably worked myself up into the panic frenzy that I was in, I've had several dogs this year in my immediate family die from cancer or freak accidents and when he started with his coughing yesterday all I could think was the worse.
I will update again next week after his second round of blood work.
Thanks to those who posted I certianly do appreciate it.