Any help with depression?

I've been feeling suicidal many times in my life and it's sparked off again today and I just feel like it's time to end it. I had a bad day at this work experience thing, then because i said about "a tramp yelled at me in the shop (i'm working at for a week)" people on Facebook started yelling at me. Then to make matters worse, my brother and dad started yelling at me over something, then i spilled yogurt all over me and said "this is the most unluckiest day ever" and my mum started laughing saying how ridiculous it was getting upset over a yoghurt and work, when she doesn't know most of the things in my life. I think I have depression because I took tests on the internet and I don't really go out because I just don't think I have friends who would like to hang out with me, so have internet buddies. I don't really want to talk about this to them, or my school friends or my family because they'll laugh (my parents thought it was stupid when my mum had to go into school about teachers realizing I was feeling down (somehow reading my mind) two years ago. I just need some advice and things so thanks :)