I mentioned this before that when DS was a couple months old he'd cough so hard that he'd throw up his formula. I'd have to hold him over sinks, floor drain... I asked his doctor at the two month well child appointment who was also head of the local cf program. He heard the cough and commented that "it's what they do, they cough".
DS was on keflex, we were already doing 4 cpt neb treatments a day... A few weeks later we went in for a recheck at the cf clinic in the city and pretty much got yelled at because DS had bronchitis and didn't we know he could've ended up back in the hospital. We were told we needed to learn his cough and to me it DID sound like a chesty bronchial cough.
I KNEW in my gut that something was wrong, DH and I argued about it because "the local doctor said he was fine"
So they ran a culture and he had some sort of enterbactor choclae bug common in nicus. Was put on several antibiotics and was fine in a few days.
A few years ago DS came down with a cold, no fever, was more tired and had a sporadic cough -- we wondered how he could be sick because he was on keflex, zithromax and tobi. At that time he got put on another abx for a few weeks. IMO, contact the doctor and indicate this has been going on long enough.