What Causes Wheezing Sensation,metallic Taste In Mouth And Itchiness Of Shoulder Blades?

Maybe once a week I have a coughing fit it can last for 20mins eventually it subsides but when I deep breathe I sound as though I have a wheeze and I have a metallic taste in my mouth I also have an itch between my shoulder blades. I have had a chest X-ray and that is clear, I am not an asthmatic and haven't had a cold or any other viral infection recently, I am wondering what this cough could be.