Baby congestion? pedialyte?!?

I have a five month old. He has had congestion for about a month now. I brought him when it first started and all the doc told me to do was use saline drops and suction his nose. Well, I need some better advice because he has developed a horrible cough. I called this morning and they said to use Pedialyte? Does this mean to stop his formula or what? Also can I use vicks on him, this young? Any other advice is great. Thank you so much!