But i'm not supposed tell anybody abt it

A scoliosis? it's when your spine makes a kind of arc to the side instead of being straight
It changes your posture and causes a pretty bad pain, and you need professional help to get it fixed, like giving you exercises to toughen up your back. I had one and had to wear a corset on my waist for 2 years to fix my spine
Tho don't get too paranoid heh-- but yea i suggest you to keep an eye on your back pains if they're really on a regular basis

What's that?

Hm... keep an eye on your back and neck, theres a chance it might be a scoliosis
As for the stomach idk