A.S.
Dear S.,
Michelle said the very things I was going to say. With my daughter, what worked best was Delsyn cough syrup and putting a vaporizer in the room. For my son, cutting back on milk products helped. Oh, and make sure he stays hydrated with water and juice halfed with water. It also sounds like it could be asthma.
Have you tried natural products such as echinacea? There is one liquid called First Sneeze tastes awful but works wonderfully! And it doesn't have the side effects that antibiotics have. It boosts your body's own immune system to fight infection.
Hope this helps,
A. S.