Bizarre. Is it Tinnitus?

Hello there.
I believe I have a form of Tinnitus.
What I am experiencing occurs most frequently as I am going to bed. It occurs only in my left ear. It is a pulsating drum-like sound; and sometimes almost as though I am hearing the blood rushing in my head. Although it only happens at night (when lying down), it is loud enough to prevent me from sleeping.

I have had a head injury and also an ear injury at a young age.

I have not yet consulted an ENT doctor, but hope to in order to rule out anything serious.

In the meantime, I wonder if anyone has a similar experience, and whether you consider this to be tinnitus.

I enjoy reading through the threads, thanks for everyone's input and discussion! I look forward to following this site in the future.