Could The Stuffy Nose And Cough Be Due To Bronchitis Or Sinus Problem?

My son is 6. Over the summer had an on & off runny nose,postnasal drip at night, and in Sept developed a cold first & after couple days bad cough, gave him 1 dose of Robitussin, and overhight started wheezing, rapid breathing..ended up at a clinic and was prescribed Ventolin & a steroid puffer & Zithomax. In another 2-3 months got over other colds without any problems, but now after 3 months almost the same problems after a cold & a dose of RobitussinDM at night. At the walk in clinic said he s suspect of asthma, even if I asked about an allergy to DM. He received Biaxin & they said to use puffers again, but I don t want to give him the steroid, because everybody has a different answer as of when & for how long to use it (answers between a few days, 2 weeks, until he s better, etc). I understand it s not for acute treatment. He s cough is wet now, spitting a bit of light dusty-brown mucus, but his nose is very stuffy, and I m thinking it s more of a synus& bronchiolitis problem? Could he fight this cough only with the antibiotic and maybe the Ventolin, or just some steam inhalations? Thank you! A.I.