I can relate. I was so shy in high school that I would take a book with me to lunch so I had something to do. I certainly didn't have anyone to talk to. It hurt. Like hell.

If I could only go back and tell that kid the good times he was in for.

But if I had to tell myself something, it would be this. Repeat after me:

MY PRESENT CIRCUMSTANCE IS NOT MY DESTINY.

It really isn't. As long as you make that realization and sit down and make the decision that your destiny is different, it truly will be.

What should I do?

You should start with a small plan. Not a goal, but a plan. From now on, you might have a goal, but it's more important to have a system.

Don't have a "goal" of making new friends. Have a system of talking to someone new every day. Don't make a "goal" of not feeling lonely. Have a system of reaching out to someone when you do. Don't make a goal of having a great social life, make a series of manageable habits you can do every week to build up this life over time.

Know how many kids have parents who put up a sticker calendar? Five stickers in a row and you get ice cream? Come up with one of these for yourself. Five days in a row of talking to a stranger and you can go get a reward for yourself. Or three weekends in a row of trying a new social activity. Whatever it is, make it something measurable and actionable, and set your standards for your reward.

Then, once you get the reward, make the next milestone a little bit harder.

Eventually, your mindset will change as a result of this action. You'll start to see yourself in a different way. You'll notice that the little things that once scared you aren't even a consideration anymore. And one day you'll look back and marvel at that one post you made on Reddit and wonder how you ever felt that way.

I'm not dismissing your current concerns as invalid. I know loneliness sucks. I've been there.

But I'm not there anymore, and I'm telling you exactly what I would tell myself if I could go back in time. So take that for what it's worth. good luck