I stopped smoking about a month and a half ago, and ever since, I've been getting this weird feeling on the left side of my chest sometimes. There's occasionally some pain that only lasts for a few minutes. Plus, I notice I sometimes get short of breath and start sweating. I've found that burping can sometimes relieve the discomfort, but not always. Once in a while, the pain starts in my back between my shoulder blades or in my lower back. Does this sound like something I should be concerned about? What might be going on here?