sohilsingh469, I'm sorry you are feeling so bad. Four months of meth will do that to you. Alcohol doesn't help, except in the short term.
I'm gonna have to agree with Kortie; 18 is way too young to give up. I didn't do drugs as a teenager (waited until college for those), but I did leave home at 15 and had it pretty rough for a while. I didn't finish high school either at the time.
All that said, it can feel so bad that the only way out is suicide. And without support from others or something that you find interesting, life is pretty bleak. So I get that.
My wish for you is that you find something that gives you the strength to keep going. (In my case, it was just plain old being stubborn.) You are in a deep valley. You can't see what is over the hill. I'll be rooting for you.
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The river is the melody
And sky is the refrain - Gordon Lightfoot