I'm convinced I'll be alone forever, but can you keep this a secret between me and you?
Why do you feel so alone? I hope you are kidding with me.
Because I know there isn't anyone out there fit for me.
There are a lot of people out there -- literally millions. You've met a tiny fraction of them. How can you be so certain you'll never meet anyone?
Everybody I've dated and been friends with turns out to be bad.
You should never give up. Keep weeding through them and eventually you will find a match that is almost perfect for you. No one will match perfectly 100% but make sure you can tolerate them as much as they tolerate you.