Help docs! i'm trying to find out what causes a child to have terrible stomache pains and migraines?

Question too big: A better history and exam is necessary. You have so many possibilities that almost every answer will be wrong. That child need a personal encounter with a qualified doctor. The history and exam will help narrow the choices. Appendix? Poor prescription on their glasses? Cancer? Where do you start guessing at the possibilities? Maybe a bully in school. Don't even know how old your child is.