Hey, my 3 years old son has been coughing since the past 3-4 months and still no sign of improvement, we took him to doctor since last 3 months ago and doc prescribed medicine for him but no improving at all. Normally he don?t use to cough during the day but at night while sleeping he always cough, though no through out the night but when he cough its very serious. And he is having dry cough. Please suggest what could be the reason and what we must do.