My son is 9 he has had a bad cough for weeks now i've taken him to the er and to his doctor for emergency visits they all say the same thing nothing ?

Cough: There are lots of reasons we cough. It is important to remember that cough is a protective reflex for our airways. Generally a cough that is associated with an acute illness (i.e. a "cold") can last for 3+ weeks - even once all the other symptoms are gone. Other reasons for cough: Asthma (all types), gastric reflux, allergies/ irritant exposure (especially second-hand cigarette), pertussis....