You're only 29 -- I have good friends in my life that I didn't meet until I was in my 40s.

You might need some hobbies which are more social, like volunteering. It's very easy to fall into work -> hacking at stuff -> sleep cycle, but you can't live inside your own head for the rest of your days.

I'm older and I've lived through the analog era, before people had cell phones or internet. Facebook wasn't around when I graduated from college, so most contacts from before that withered away -- especially if you ended up living in a different state or city.

It is sometimes heart wrenching to hear about people from your past, knowing that you didn't keep in touch. A girl that I went to elementary school with, always kind of an odd girl (but in a good way), developed leukemia in her 30s and passed away in 2019. I didn't know for seven years. Seven! I went through her Facebook page and it was a roller-coaster of emotions, playing her life backward as she chronicled her condition worsening, periods of hope, all the way back to when she was saying that she had some kind of bug and felt awful.

She was a good friend to me in elementary school, but we ended up going to different high schools and different directions after that. I feel bad that we didn't keep in touch, and that I was completely unaware of her suffering.

I can't wallow in this, though, and this is where I'm attempting (maybe poorly) to make a connection to your situation. You can't change the past, but you can start making meaningful attempts to forge new relationships and to rekindle old ones. Those people that you never kept in touch with? Reach out to them, if only to say "Hi". Reach out because you want to do it, and not because you need something.

How many days will you sit there and think "why doesn't anyone reach out to me?" when you, yourself, are not also making the effort to do so?