4 month old- COLD

So I took my 4 month old to the doctor 2 days ago and they said he seems to have a cold. The said I can’t give him anything and it just has to run its course. But his cough has gotten so much worse today. He SCREAMS when he coughs, he is only eating 2-4 oz every 4 hours and is extremely tired. When I called yesterday they said to just use saline drops and get a humidifier and it will go away on its own. He’s not really congested he just has a HORRIBLE cough and I’m guessing a sore throat... I’m just seeing if anyone else has gone through this and if anything soothed your little ones because he is in obvious pain and discomfort and it’s breaking my heart.