I had repeated success. Mullen oil w/garlic was what worked for us. Many doctors are avoiding antibiotics as they are not the proper treatment, but western medicine doesn't have any answers and they don't want you to leave empty handed.
If your child is eating lot's of milk, cheese or white flour these can be cause of the congestion.
Since you are seeing a Natropathic doctor, you have most likely already been given the advice to take probiotics to balance the antibiotics.
One of the best books I have found is Eat Right for Your Type. Even though we have different blood types in our family, we all thrive and have worked it out.
If you child is a blood type O, milk, cheese and flour are among the worst foods you can feed them. I grew up in constant pain, until I found this blood type information, now I am healthier at 45 then I was at 15.
Always do your own research. Doctors have a limited amount of information and are under untold stresses these days. Take responsibility and participate with the practitioner...you have to live with the results.
Garlic and Mullin oil have been around a very long time.