In France there's an illness recognized by medicine that other countries don't, it's called "Spasmophilie"
It's not a disease by itself, but it has symptoms of other diseases, feeling oppressed, depressed, stressed, throat ball, feeling out of this world, feeling passing away without passing away for real, anxiety, etc.
In america, it's called (and limited to one syndrome) "Hyperventilation syndrome".
You can check the
symdrome list on the french wikipedia.
There's nothing to do, and it can last few years. (My mother had it for 10 years)
And one day, all is gone.
It's mostly like depressions.
if you are hyperventilating, usually it's recommended to breath in a paper bag to make CO2 rise again in your blood.
Don't do stupid things like suicide, just take on yourself a little and wait until you feel better.
it may sound like a stupid advice, sorry
Like said before too, it's usually the age where you can feel bad, don't worry too much, cry a lot if you need to.
you'll feel better again.