I want to help you. Really, I do. However, in order for me to try and offer any advice at all I'm really going to need you to explain in a bit more detail what it is that's making (or has made) you feel this way - if you have any idea at all, then explaining to me why might help me help you.
Killing yourself should be fun....then you can leave them all notes on why you killed yourself. Tell them all they things they never did and should have done. Tell them that you will never forgive them for they pain and suffering they caused for you. 
Why can't you tell them now? Why do they need a suicide note? You can't do much with a suicide note, other than regret and wish things were different. If you go to a person (IN person, not by a suicide note) then that's when things can be changed and made better. If people aren't doing things that you need or want them to do, then it might help if you actually tell them what you need. Life would be a lot easier if people just knew when we needed things from them, but that's not how it works. Again, I don't know your situation, so I don't know how possible it is for you to ask for help, but truly, people can't help you unless you reach out and ask for that help. It can be the hardest thing in the world to do, but sometimes there's just no other option.
I'm getting that you've been hurt by people, and I do want to offer advice and help where I can. I just don't know what to say or where to start - I don't know what your problem is so I have nothing to work with. I'm here though, if you need to chat.
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it's broken beyond repair. it's in a million little pieces.