Why do my lungs hurt and shortness of breath after smoking?

I'm only 27 and I don't smoke often. Socially mainly, and maybe a few a day. When I go a while without a cigarette, I develop a pain and rash on my lung. I'm also out of breath. As of right now, I am really out of breath and haven't smoked in 2 days. I only have one cig left but I'm afraid to smoke it right now. Also, my coworkers are in the 50s/60s and smoke 3 packs a day yet seem to not experience shortness of breath or lung pain. Why am I? Could I be developing something bad?