I can most certainly relate to what I have read here! The other day I impulsively decided to take a walk. I usually just walk out to my mailbox, which is about half a city block away. Just doing this sometimes gives me shortness of breath and chest pain (muscular) When I decided to take this walk I was feeling just so-so, not great but I did it. Three days later, I crashed big time. Heart palpitations, chills, mouth sores, unable to get out of bed, weepy...it was awful.