Take him to a different doctor. Your child is painfully honest at that age and the doctor shouldn’t dismiss that. Especially when your child’s complaining of pain in his bones.

I was like this as a kid and it took forever for a dr to listen to me. They eventually said I had Psoriatic arthritis.
I’d definitely keep taking him to different doctors until someone takes it seriously.

I would get a second opinion

Take him to a diff doctor maybe? Some docs dont listen🙄