Welcome to HCM
It is good to know that you have stopped smoking
,for which please accept our congratulations,but remember to keep your will power.
Why are you having shortness of breath
,may be you are having spam in your airways along with inflamation in airways or some kind of allergy
Other thing which is possible is some inflamation because of infection or trauma causing obstruction in throat.
You should visit a Chest Physician and ENT surgeon to know exact cause of breathing difficulty so that it can be treated
After examination a X ray
chest,Indirect or direct laryngoscopyand PFT ( Pulmonary Function Test) will help to diagnose your problem and treat accordingly.
Good Luck to you.