Jess, I'm so sorry to read your posting. I'm also new here, this is my first posting, and reading your posting was so hard, because you're so young.
I'm 52 now, but at your age, I felt the same even back then, and tried to act on it, and was stomach pumped. It had been a build up of events, and like you, had lost friends far too early. One of them had committed suicide, and after the stomach pumping, I felt so thoroughly ashamed, because had seen the hell that his parents had been put through. Some days, even now, I wake and wonder what the hell the point is of getting through each day, but I have a young son to stay around for.
It does help putting things down, and if you don't feel that you can do it on paper because of someone finding it, then do it on a private document on your PC, which presumably is your own? And you always have this Forum, which seems to be wonderful because everyone's in the same position.
Go to your doctor, my darling. It's the first step and it's not easy, but once you've done that, you'll feel better just for having taken that bull by the horns. Go with a friend who knows you well, and understands what your problem is, and wants to help. Sadly, not all friends understand that it's a depression issue and just have us down as 'Moaning Minnies' who 'can't get their act together' and tend to avoid us, which makes it worse. Makes you feel even more excluded.
I only went to the doctor within the past two years, really, and that was because I thought I had the onset of Alzheimers - my concentration was shot to pieces, couldn't focus, and had become paranoid that I was being singled out for bad treatment at work - but it wasn't Alzheimers, it was depression striking again. If you've got these symptoms my love, then you do really need to get help because it may impact your exams. Do you have a Youth worker or Connexions, etc, that you can talk to? You'd be amazed how many times they probably have to deal with this situation, and Jess, there's no shame in asking for help. xxx