Hi Lisa,
Its great that your Dr gave you meds for your son and seems to be helping but you mentioned that he still have a cough. If you want a good OTC med I prefer Delsym for my kids, it really works great.
On the other hand my grandmother showed me a home remedy that works everytime and my kids litterally beg me to make it when the cough season starts up. Take a medium sized red or yellow onion, peel the dry skin off and cut it up into medium to smallish chunks, no need to finely dice it or anything. Put it in a small sauce pan with 1cup of sugar and bring to a boil over meduim heat. once it boils lower the temp to medium low and stir frequently if not constantly until the sugar glaze is trasparent to clear. It will be yellowish or reddish in color depending on the onion you used but it should be clear or easy to see through. Remove the syrup from heat and let cool. I give the kids 1 to 2 spoonfuls of the syrup, not the onions, every 3-4hrs for their cough. I strain out the onion chunks and store it in a jar in the fridge although its easier to dispense at room temp.
I don't know why this works but it does and suprisingly it tastes good too! Good luck, you've got the rest of the winter to go!
C. C.