Bumping up...I see you posted again.
Have you been to a doctor about your racing heart? Just trying to figure out what you've been diagnosed with. There are times I wake up gasping but it feels like I'm holding my breath. Sometimes my heart wakes me up and I have been diagnosed PAC's, PVC's, and tachycardia (racing heart). My heart has been monitored at its fastest, 160+ beats per minute, during my sleep. Actually, for the past two nights, my heart has woke me up. I have also had nocturnal panic attacks. If you haven't been checked out by a doctor, it's always best to start there. There are so many things that can cause your heart to race...certain foods, medications, caffeine, alcohol, tobacco, stress, anxiety, and sometimes just eating anything will make mine race. Also, sleep apnea can cause your heart to race. I also can't fall asleep on my left side, but when I'm on my right side is when my heart wakes me. I know it's very frustrating for you. Keep us posted on how you're feeling. Best to you!
Bumping this question up as it has been moved. :)