Does anybody know why I am experiencing pain & tightness across my upper chest but mostly on my left side? I am having a hard time telling if it is my breast that is hurting or if it is my heart, or if maybe it is just related to the muscle pain around my shoulder blades? This has lasted for a number of days, is worse at night, and painkillers don't help. I have been taking the antiinflamatory Naproxen for 4 nights now for a different reason and am wondering if it could be a cause? I know chest pain can happen when you panic, but for me it is the opposite -- I feel the chest pain and THEN I panic!