There is no particular reason to believe "it's something serious". It might go away with growth.
As long as they are isolated episodes but you feel generally fine, you should be optimistic!
It doesn't mean it's only in your head, Unfortunately Medicine can't diagnose everything right away.
Feeling faint can be cause by Orthostatic Hypotension (when you get up in the morning or stand up suddenly). Feeling shaky can have multiple causes, if it gets frequent (chronic) you should see a Neurologist.
Hello~At your age, it could very well be a fluctuation in hormones. I would ask the doctor to do a basic hormone panel, sometimes this can give an idea of what is going on.
You may have a few things, vertigo or something more serious. It can also be hormones as you are at the age of great cahnges in the body. Get tested for vertigo, hormones checked and if that all fails ask for futher examinations.
Also if i am feeling faint is it dangerous for me to sleep?