I would definitely take him back to the doctor. My daughter has had lingering coughs and they got so bad she would gag on her food and throw up b/c she would break out into a coughing fit while she was eating. She also wasn't sleeping at night b/c of it. Her pediatrician gave her Orapred, also known as prednisolone. I was a little worried about giving her a steroid, but 3 days of it, and the cough was gone. Finally some peace for my baby! It has worked for us twice now-- she had RSV when she was a baby and is now prone to catching coughs and may have asthma. I am so thankful for it. We had no side effects from it whatsoever. The stuff pretty much worked immediately.