Sass;
First of all, WELCOME to SR!
Now, I cannot tell you if it's normal or not. I have the start of COPD, and have the same problem catching my breath occassionally. I know my capacity is down, because I sing, and it's effected. I've been quit almost 3 months now...and I smoked for 36 years.
Talk to your doctor. But, the good news is, I've caught my problem on time. There's still the opportunity for my lungs to heal themselves with time. At the very least, they won't get worse...
Keep the quit and post before you puff!
Shalom!