Well, I think you mentioned once that you believe you have ADHD? I have ADHD and I believe it is the cause of my brain not shutting up. (Technically ADHD can cause racing thoughts from time to time.)

When I was a kid, I used to hear things. For example, I would hear my dad call my name and tell me something... But he either wouldn't be home or he would tell me "I didn't say anything." Same thing with my mom.

I also tend to hear things when I'm extremely anxious. For example, I might hear someone "breaking in" through my front door, but it turns out that maybe the A/C kicked on... and sometimes the sound is totally made up in my head