Coughing in the morning?

I am 21 years old man.Recently i had a cough and now is about going to 2 week that is every morning.Its start coughing when i forcefully exhale and sound like wheezing in the chest.But when the the afternoon come it sound reduced.I had X-ray and comple blood count test and the doc said it was clear.When i talk about asthma the doctor said it wasnt becouse they cud not hear any wheezing.It just becouse the wheez occur in the morning.Sometime it feel like itchyness inside the chest.I afraid that it cud be someting worst or just a common thing happen.help me.