Fab, if you read my thread from sunday (linked to on the thread that you posted on) you will see that I had EXACTLY what you are describing now...
Started off as a pain in my left shoulder blade, right at the bottom. I have been worrying about heart attacks recently anyway, I managed to convince myself that I was imminently going to have a heart attack or was having one. I sat at the top of my stairs, feeling freezing cold, clammy, heart thumping in chest. I went straight to A+E where they sent me straight through and wired me to an ECG. They could tell immediately I wasnt having a heart atatck or anything close to. They put me on a heart monitor and my heart rate was at 131
so that made me even more anxious... But it was anxiety that started the palpitations in the first place. The doctor diagnosed me with pleurisy. I'm not convinced I had that. It was more than likely a pulled muscle/pain from bed-sharing with an ill 4 year old who takes up the entire bed! It has gone now, totally.
You are working yourself up, my love. Take it from one who knows. If you are genuinely worried, go to A+E. Don't worry about time-wasting if you think it could be something. Just being told that there is nothing up with your heart can be enough to calm you right down. When they told me my heart was fine on sunday, my heart rate went right down to 89.
I DO suffer with HA. Only realised it this week and have no problem admitting it. I'm not saying that you do or do not. But I definitely think you are winding yourself up here.