I am a smoker of about 9 months now. I usually only smoke about a pack a week.?

I have developed a cough over the winter that lasted a good 1-2 months. I went to the doctor and was told it was post nasal drip. They gave me meds which never seemed to do good. It eventually went away. Now I'm here in June and I have sickness again, which was determined by my doctor to be acute bronchitis. I know that I need to quit smoking, as that seems to be the only way I can kill this thing. Does anyone have any idea as to what could be wrong with me? Is it really just acute bronchitis, or could it be something more? please help!