Thanks to everyone for your replies.
I’ve been experiencing it intermittently, and I know this might sound silly, but for some time I didn’t realise it was tinnitus and thought it was external noise from outside my home. Initially I only heard it at night, but now it’s becoming more frequent and I’m hearing it during the day too – standing and sitting as well as lying down.
It’s normal to hear your heartbeat in your ears from time to time, eg on exertion, in stressful situations or when you’ve had an infection, but when this is happening regularly it needs medical investigation because there may be something serious underlying it. It is usually caused by increased or turbulent blood flow or a greater awareness of normal blood flow.
My blood pressure is usually normal, and sometimes a bit low. Over the last year I’ve noticed my pulse rate is often below 60. I’ve got an appointment to see ENT in a few weeks.
Snowathlete, I too feel like my heart beat shakes my body at times. And I also feel like the blood is surging through my heart/chest sometimes, especially when I’m in bed. Weird sensations.