Has anyone else's baby had a cough/congestion that just hasn't gone away? My son is 3 months and I…

Has anyone else's baby had a cough/congestion that just hasn't gone away? My son is 3 months and I swear he's had a cough and congestion since he was born. At first, they just said it's the amniotic fluid clearing out and it's normal. Now his pediatrician is saying it could just be from allergies and it's probably nothing to worry about and to just keep an eye on it. He doesn't seem to be bothered by it but it just seems so strange to me for a baby to have a cough this long. I made an appointment with a pulmonary doctor on Friday just to play it safe and I'm nervous :(