The Storyteller by Brandon Hobson

From Scholastic Press:

Ziggy has ANXIETY. Partly this is because of the way his mind works, and how overwhelmed he can get when other people (especially his classmate Alice) are in the room. And partly it's because his mother disappeared when he was very young, making her one of many Native women who've gone mysteriously missing. Ziggy and his sister, Moon, want answers, but nobody around can give them.

Once Ziggy gets it in his head that clues to his mother's disappearance may be found in a nearby cave, there's no stopping him from going there. Along with Moon, Alice, and his best friend, Corso, he sets out on a mind-bending adventure where he'll discover his story is tied to all the stories of the Cherokees that have come before him.

Ziggy might not have any control over the past -- but if he learns the lessons of the storytellers, he might be able to better shape his future and find the friends he needs.