I have a cough and a wheezing sound when i breathe. no other symptoms, phlegm is clear. what could be wrong? ?

Reactive airways: It's quite possible your airways were irritated by something -whether that was toxic smog, tobacco smoke, or a virus causing a bronchitis. The wheezing is caused by irritation in the airways which affects the flow of air, causing that sound. You should see a doctor, especially if you've had this in the past- since this problem can worsen, especially at night. Albuterol is often a quick fix. See MD