For The Past 2 Months I Have Been Having Problems

For the past 2 months I have been having problems breathing. I have had post nasal drip this whole time and there is congestion in my chest, however I have not been sick at all or had nasal or sinus congestion at all. I have improved somewhat since 4 or 5 weeks ago when I would wake up gasping for air. I started exercising this week and sometimes I still feel short of breath and sometimes it's much better. Not sure why. As a child I did have exercise induced asthma and I am a 43 year old former smoker who quit 4 years ago. I am worried that I have had this much trouble breathing and chest congestion without being sick...what does this suggest? I am getting a pulmonary function test later this week.