Follow a DID system through life

I have this book in my head that I so want to read but I can't find it anywhere.

It's a book where you follow the main character through their day to day life. This main character had DID (dissociative identity disorder) so you follow this system and everything that is going on in their head.

You follow the system trying to hide that they're a system from the host but eventually the host finds out. Then they have to learn to live it without having to hide.

PLEASE TELL ME SOMETHING LIKE THIS EXISTS!!! I really want to read something like this. Please help!