I have had chronic barking cough for more than 3 weeks and have seen two different docs. One said possibly beginning of bronchitis the next one two weeks later said allergies. Cough syrup, musinex, lozenges, a course of prednisone, benzotate, inhaler and nothing seems to help. No fever but fatigue and headache and metal taste when coughing. They both said my lungs are clear. What can it be?