Get yourself a second opinion. Yeah kids cough but not constantly. I have learned that sometimes docs just don't listed! I have a wonderful Ped doc in Orlando, she listens. She is a mother and knows that mommys know when something is wrong. Let me know if you are interested and I will send you her information.
My son is 3 and has severe asthma, because his ped and pulminologist never gave up and always listened to me we finally got him on a good regimen and now he has not had an attack in months! Not only did he have asthma but he had reflux, causing the night coughing and irritating his bronchial tubes worse. Thank god for docs that listen! Take care of you and good luck.
Oh yeah, god bless you for being 42 and trying for another. I am 35 and 5 months along, dang I wish I was 25 if ya know what I mean.
T.