I started coughing late July as well! Almost got better then slipped back.pain near sternum and under right breast is felt when I cough, sit up or change positions. I'm no doctor, but i am familiar with bronchitis. I feel that the metallic taste you have indicates infection of your respiratory system. Doctors don't like to prescribe antibiotics for bronchitis but they have always worked for me in the past. This time, they did not prescribe antibiotics and i have suffered for it.I finally convinced them to give me a zpack and my cough started clearing up then came back after the humidifier was too high on my CPAP machine...my unofficial advice...get an antibiotic.