When i lay on my back, no matter the position of my head i feel pressure in my face, head, and neck and can feel my heartbeat in my neck and face why?

TOS: One possibility is thoracic outlet syndrome which is a condition that involves pain in the neck and shoulder, . The thoracic outlet is the area between the rib cage and blood vessels and nerves coming from the spine or major blood vessels of the body pass through a narrow space near your shoulder and collar bone. Consult your physician to rule out this condition.

Need more info: See your doctor and get this worked out. Cannot make a diagnosis from long distance.

Get evaluated: There are many possibilities from the trivial to very severe -- you need to see your doctor.