73 yr. old male. I walk for an hour or more daily (14 min. mile). For 4 days now, I started with a fever, sweats, and aches......felt ok next day but extremely tired but no fever. Gave up walking for 2 days. Only walked a slow mile on 3rd day. Picked up pace on 4 day (today), and across my upper chest felt pressure and tightness. After a short distance, I started to sweat profusely and felt nausea. Home now, and feel ok, slightly lightheaded. I have MVP and mitral regrurgitation, all my ECHOs have been fine. Should I be concerned? Thanks