Was just reading an article in a Reader's Digest today about this symptom! The doctor found a very small hole/tear in the patient's eardrum that was causing him to hear his heartbeat louder than anything else.
Please see an ENT or ear specialist. Wishing you the best.
Sometimes I do that when my thyroid is off. My heart pounds in my back. Kinda strange!
I ha the same problem until I was diagnosed with hypertension or really high blood pressure. I was put on a med called lisinopril and it fixed that problem within a week. The ringing in my ears stopped too :)