Sorry to hear you are having such a rough time with your pounding heart. Does it stay in rhythm when it is pounding? This may not be Afib but something else. So, it always happens when you are lying down. Google this. Are you lying on your left side? When I lie on my left side and not my right, my heart beats harder and I am aware of it (but it is not pounding hard) and so I shift my body a bit to unsquish my heart. It doesn't sound very technical or medical. but it works. If you get up in the night once it starts to pound, does it stop or it continues. Does bearing down help?