Actually sounds like you are suffering from gerd (acid reflux). Not all of your symptoms match, but quite a few do. Gerd can cause the palpitations, especially after eating and lying down. It can also cause quite a bit of back pain.
Try cutting down on smoking, alcohol, caffeine, tomato based foods, chocolate, and citrus anything. I know it sounds difficult, why don't I add a vow of celibacy to all that too? But, all those worked for me(except for the celibacy thing of course).