I have a 5 yr old Pom (the big size, not minature). He has constant heavy breathing. Matter of fact the only time he doesnt is when he's laying with his head down. As soon as he lifts his head the heavy breathing starts. He also has that honking cough and coughs til he throws up. Reading about this "collapsed trachea" it sounds like he may be one of them, but the vet has never mentioned it or acted like it was a concern. They only ever said, he needs to lose weight. I'm having a hard time getting him to lose weight. Can you suggest what dog food/brand I should feed him, and how much/often?