My thumping heart beat distracts me 24/7, especially when I'm trying to concentrate on something else like a book or schoolwork. I've tried so many ways to alleviate this obsession, without success.
Have you had a cardiologist check you out? I taught CPR for 10 years, and learned to take such issues very seriously.
If the MDs gave you a green light, then perhaps meditation can help you change your focus. Even the breathing exercises I do during yoga help me to focus my mind.
I hope you get some relief!