s possible that the lungs ARE clearing and your not aware
of it because
of the continuing cough.....
In this case, the Antibiotics are doing their job....
First thing tomorrow, I would contact the Vet and #1- Get a Cough suppressant, #2 - Inquire into the need of another chest xray to see if the cloudiness is any better, thus the Antibiotics would be working..........Let us know how he's doing and good luck.......