I feel you. The fear of being alone is natural, it is uneasy because you are forced to confront your true self. It takes a while to get used to the lack of the social cushioning, but you don't have to do it all alone drastically. First thing you need to address is the fear of being lonely - the root cause is lack of self dependence. Or rather, too much social dependence. You need to (slowly) learn to be comfortable with your self. You do that by not looking at it like a punishment. It is just being at peace.

Having said that, I always like to join hobby groups on meetup.com (say cycling or DIY crafts or book clubs) and get to meet new people that way. It helps. The other thing I love to do is attend conferences or tech talks. It really removes that feeling of being lonely and since you do it on your terms, you will come to a point where you realize loneliness is just a choice and you can be around people whenever you like.

Also, look into real passion projects - you can spend time working on stuff you love to do and it will offset any emptiness you feel. I love working on my car and speaker building. Some of the projects can take years and I will spend one weekend or a random weekday working on it. It really turns being alone into an advantage.

When I felt alone early in my career, I used to go to this shared office space near my house or WeWork once or twice a week and surrounded myself with people there. It helped a lot. The day you realize you can live with yourself without needing anyone around is when you will also start feeling less depressed. People come and go, you are the only one for yourself.

Hope this helps and if you ever feel like talking to someone, don't hesitate to shoot an email (in my profile). Always love to meet new people :)