I also had shortness of breath and just energy after quitting smoking. I had smoked for about 10 years, half a pack to a pack daily. Two months later, completely nicotine free, I feel like I have caught every sickness that has been going around the office. I wonder if this could be from stress or my immune system being overworked from trying to clean out my lungs? Also, could my smoking had suppressed allergies in the past? I still am glad I quit smoking and don't want to start again. I'm really hoping that with time I'll be as good as new!