I used to feel intensely lonely until my 30s. I made significant efforts to get out there and socialize. Something changed and I'm now considered a very extroverted person by others. A few things clicked inside me. Some books you may want to consider:

1) Dale Carnegie's how to win friends and influence people book.

2) The Game by Neil Strauss(friend gave me a copy .. this is about pick up artists, something I never did but it was influential in some way)

3) Surely you're joking Mr. Feynmann

All these books have something about being social. I make it a bit to get to know strangers (on planes, uber rides, whatever). I almost think of it as a missed opportunity if I don't have an engaging conversation with people. Many are strangers and I'll never see them again, so if I say something stupid, whatever. I guess that is the idea I got from The Game.

I still suck in group settings socially. I feel incredibly awkward. But 1-1, I am actually impressed with my transformation. I was super introverted until exactly 30. I guess one other thing that changed is if someone invites me to something social, I always came along, and I kept a smile on my face. This was exceptionally easy to do in NYC (getting invites to hang out with people I mean).

I also have to say, friend, you must love and respect yourself, first and foremost. I felt some pain in your words. Look .. we all have done stupid things we may cringe on in reflection. My addiction is tech and online shopping. I try to do my vices in moderation. Don't judge yourself too harshly. We're all imperfect humans. Good luck to you.