Just a warning on the heart x ray....regular vets are not schooled enough in this area to know the specifics of every breed. They literally go by an image chart for comparison. It's likely this second vet will tell you the same as the first.
Some advice I'd offer you...when you are at the vet's if you do not understand what they are telling you....make them explain it until you do. Remember you are paying them....
Hopefully it is kennel cough and with proper treatment it will go away. Sometimes that takes awhile though.
Good luck.