Smoking for more than 10 years may or may not cause permanent damage to your lungs. Being more out of breath than usual with exercise strongly suggests that your lungs are susceptible to the harmful effects of cigarette smoke. You have made an excellent decision to stop smoking immediately!
Only time will tell if the smoking has caused permanent damage to your lungs. The effects of smoking that you have noticed with exercise should become less pronounced within 90 to 180 days of quitting smoking. If there is no permanent damage to your lungs, your breathing will return to your pre-smoking condition.
You may want to look at our Quit Smoking Topic Center at http://www.nationaljewish.org/topic/smoking_cessation.html for ways to help you to quit smoking. Also check with your doctor for other quit smoking resources in your area.
Good luck!
You may wish to see your doctor for an evaluation to see if you have asthma (which is also helped by stopping smoking & avoiding lung irritants).
Take care & good job!
Starion