Why is it that when I lie on my back after lying on my side, I can hear loud whooshy heart beats of what sounds like ultrasound baby's heartbeats in my left ear for a few seconds and then it quietens down so I can't hear it anymore?
This is all to do with blood flow readjusting itself when you change position and is of no particular sinister significance.
It can also be due to a temporary increase in blood flow from the muscles of the neck in readjusting your position.....again no big deal.