What can be the reason for chronic nausea? i've tried every test possible everything is normal. i still have nausea 24/7?

Some thoughts: See a gastroenterologist, and make certain that the GI tract is not the source. Next step, cover possible inner ear problem, perhaps ENT. If no success, consider perhaps underlying migraine tendency, with neurology. Handle symptoms with OTC ginger root powder. Hopefully, you have an involved doctor who can orchestrate all of this.

Functional disorders as well as anxiety or eating disorders are always to be considered among others, somewhat more difficult to diagnose. Your pediatrician would be best to further escalate workup.

It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor and discuss if you may be depressed. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!