Why does the voice in my head never stop?

From the moment I wake up, I hear what I think is my voice in my head. Even now, I hear it saying every word I'm thinking. When I lay down to sleep, I think of weird and crazy things, and the voice will never stop talking. I don't know if it's me thinking. It never stops. I'll lay in my bed for hours just thinking about weird stuff. I should mention that I talk to myself a lot: mostly in my head, but out loud as well.