What Causes Persistent Cough And Chest Infections While Being Diagnosed With COPD?

I'm 45 female recently diagnosed with mild COPD, I have been sick since April 2014 with a constant cough and have had at least 7 chest infections, I'm currently taking ultibro inhaler, pulmacort, and ventilan, I've been on oral steroids for 6 months on and off my chest xray 2 months ago came back normal I'm in a lot of pain could you shed a little light on the subject for me please