What Causes Severe Cough Along With Difficulty In Breathing In A Child?

My nine year old son is suffering from cough from last ten days.whenever he feels like coughing he goes to wash basin and while coughing mucus comes out and my boy feels discomfort in breathing. His TLC count is 12200/cmm, poly is 68%,lympho is 30% ,eosino is 02%,mono is 00% and baso is 00% .please make me clear what has happened and what to do to cure my boy out.