very sick Fonzie

Fonzie started coughing in the night a few days ago, then coughing occasionally in the day time, and then yesterday he looked so listless I took him to the vet. His shots are up to date, so not kennel cough. Dr Khaled thought it was something like a dog flu, and said he needed TLC and rest. This morning he was worse, had stopped eating, and didn't want to walk. Dr Khaled gave me antibiotics. If he's no better, or worse tomorrow, he has to go back, It's awful seeing him so weak and clearly suffering.