I've experienced "feeling" my heart beating everywhere,...in my chest, my neck, my head,...
I even, on occasion, "see" it because it beats so hard that as I try to relax, my chest moves up and down to my heart beat, as if my heart is beating right through my chest.
It can be unnerving, but I've experienced that since I was a child. I'm now 50.
The power of deep breathing and breath-control exercises helps a lot.
M.