Why is my mother's chronic cough and cold not improving?

My mother is 57 years old. She has been suffering from chronic cough and cold for the last three years. Her nose runs constantly with a watery discharge and she has dry cough which causes chest pain. A chest physician examined her recently and she underwent blood and urine tests and chest x-ray. She is not diabetic. The doctor prescribed capsules broncho-vaxom for three months asking her to take them continously for ten days with a gap of 20 days in between. At present she has completed one month's course but there is no improvement. Kindly suggest what to do and how to proceed further?