How do i know I'm depressed?

Depression is a horrible serious mental illness that some people(10% of the UK) go through.it makes you feel sad,misrable and makes you feel that you've got no reason to live which is very harmful.if you've reached to this moment and cant take it any more i advise you to get HELP,not do anything you'll regret.I know how it feels and believe me its very tough and im still going through it because i just dont have the guts to tell someone that i need help but forget about me if you need help you ask for it DONT BE TOO AFRAID LIKE ME, its just TOOO hard to take in for anyone!!