Is it normal that i can't think in public?

I am constantly in my head. I always make up conversations in my head. When i'm studying, i explains terms and concepts in my head as if i'm talking to someone. I'm pretty good at remembering things, i don't know if that's why, but when i'm in public, i turn into a completely different person. I think at all. I feel like i'm too aware of what's going on around me to think. Is that normal?