Will Smoking 3 Cigarettes A Day Effect My Running Capabilities?

I'm a 15 year old male, I got my heart broken a little while back and have been in a state of constant depression ever since, because I love my ex-girlfriend. I started smoking less than a week ago, because I need something to help me deal with the stress. I smoke about 3 cigarettes a day, I've only smoked 8 cigarettes total. I don't have much upper-body strength, but I have very strong legs, I run faster and longer than any of my friends, and I take great pride in this. Today, I tried to do some running, and it seems that I can't run nearly as fast or as long as I could not even a week ago. Could the cigarettes have caused this already? I plan on joining track next year, if I continue to smoke in moderation, and do a lot of running in order to stay physically fit, then would I be able to smoke and run like I used to, or will the cigarettes inevitably keep me from running like I used to? If I stop smoking now, will I still be able to run like I used to, or has the damage been done? Thank you for any help that you may have to offer me.