When I lay flat, left side of neck pulsates visibly with heartbeat. I can feel heartbeat over whole body. Visible heartbeat on chest too.?

Physical. Always start with a standard history and physical exam/lab. I suspect you either have benign hyperkinetic circulation or high blood pressure, less likely a thyroid issue. See www.thepmc.org website to clear the 1st 2. HRS, MD, FACC.