I'm really similar and haven't really solved the problem yet, but have taken big steps forwards to where it's more possible now.

The first thing I did was force myself to do something with a new group of people. It was terrifying, the thought of it, but the actual event was fine. I also began to volunteer. It took me a while in therapy to make little steps and work towards those things. They were so close to being impossible once (back when I couldn't even pick up the phone and make a phone call), but they are possible.

I think it would be a good idea to work towards social activities. Something where you're doing a task and not having to focus too much on other people might be a start (even if it''s not something you can do right now, or even soon). It might be something to work towards. Lots of cities have all sorts of groups, like craft groups, or even movie or theatre groups, where people meet up and all go along together.

I don't really know how to progress to having proper friendships as I seem to be very good at being an acquaintance (perhaps I'm just too fussy about who I really like and want to spend time with). But I do know that it's possible to move from being absolutely terrified and incapable of taking a first step, to actually taking many little steps. It is really, really hard, but it's possible.