honestly, dude your 18...i know i'm like 22 but serious at 18, 19, 20, 21, 22, 23, etc. life is still gonna suck. Unless your a frigging billionaire, life sucks ass through a straw from a 50ft. cup. The most you can do is cope. Killing yourself is the easy way out. Take it from me, enjoy your life while you can. And honestly, if you wanna kill yourself then do me a favor before hand...take a trip to various place in your city/state and compare your life to those in various parts. I recommended this to a friend once. When you look at the lives of others, primarily ppl some what worse off than you, you see that your not the only person with a shitty life.
The way I look at it, no one knows for sure whats after life, so treat it as if there isnt anything afterwards and make the best of it. In your situation, I would find a job and build up a bit of money to get a quick degree and start a career. Since you're 18 look at how much life is left, estimating lets say youre about 1/4th of the way done. You can still do any fucking thing you want to. I finally got motivated enough to get off my ass and do something to promote my future and lead to a brighter life, in the last 2 months I've accomplished more than I have in the last 2-3 years, and its built up so much more confidence and potential. You could see a doc about some of this, you could have a depression/mood disorder, which is very hard to overcome on your own