I don't remember my childhood and I'm worried about it
What is so worrisome about that?
I don't know much about me as a kid and I sometimes worry that there's no such thing as childhood memories.
Your childhood was quite some time ago. It is normal to forget things as life goes on. You can't be expected to remember everything that has happened in your life.  Just focus on those memorable moments that you can bring to mind.
I think I'm feeling better now.
I'm glad that you aren't worried any more.  It's true that some people can retain lots of childhood memories, but you shouldn't be concerned if you can't do the same.  The majority of us can only really remember a few bits and pieces of childhood.