I use to be like that... I felt like no one understood me and I was completely alone. I told my therapist this and she told me everyone feels that exact same way. Which seriously didn't make me feel better at the time. I thought she was a bitch.
But yeah, most people do feel like the world is crashing. Seriously, I've been there. Like everything in your journal was where I was a couple years ago. Honestly, struggle through it. No life is meaningless. Even if it's something as small as making a friend smile to something as big as curing cancer, your life matters.
And go to whatever means necessary to make sure you see every day. I guarantee you it gets better. It doesn't matter if it gets better by prescription right now or with great friends, it'll get better. If you ever need someone to talk to, drop me a line. I have no life and I'll be here to talk if you need me. Just don't give up. Your life does affect people. And the loss of it affects people even more.
I know you don't know me all that well yet, but I talk to people about this stuff all the time.
If you ever need me, I'm here.