Walking for a long distance is a good way to keep respiratory system strong. I heard that respiratory system starts cleaning process for lungs in early morning 4am to 6am. Its a best time to do exercise during this ideal hour :). I usually do in evening 6pm while coming from office.

@Michael117american bro i have the exact same problem and no doctor can tell me how to fix my problem or neither do they know what it is.. i have the same symtoms as u. i cant take a deep breath without coughing. do u have the same symtom?