I had chronic bronchitis and cough for about 6 weeks... i began to get sharp stabbing pain in the right side of my back now every time i cough. why?

Cough: chronic cough and now right sided back pain is concerning and requires further radiological investigation. There are may be multiple causes, including something as simple as musculoskeletal spasm or rib fracture to more complicated such as pneumonia or lung abscess. You should see your physician and have x-Ray or ct scan of chest done

Excessive Coughing: Bronchitis leads to heavy cougs to loosen the build up in the bronchial tubes. This can strain the muscles of the chest, abdomen and back and just like over-exercising any muscle, these muscles become sore. It is intense coughing often for many weeks (My recent run was 10 weeks). OTC Mucinex (guaifenesin) can help improve the results of cough & decrease need to cough since each cough is more effective.