It's a lot easier to talk to people if you have something to say. Finding a small back-room volunteer role is quite good for this, especially if you're the only one doing it. For example, it would be daunting to volunteer sorting stuff in a charity shop if there was more than one other person working there.
Things that have helped me at various stages -
being more judging
- ie, if I'm worried what someone thinks of me, start by seeing what I think of them. Start noticing when the faux pas of others and don't keep going over in your head your own faux pas.
looking out for people worse off than me - the person at the fringes of the room too scared to talk to anyone - there's a good chance they might be pleased to talk to me
doing voluntary roles which mean people have to come to talk to me to get information they want. After someone's come to you 5 times for a copy of the Agenda, you might find yourself in a conversation about the weather 
No, you haven't let shyness ruin your life. You've done a great job of keeping going, supporting yourself financially, despite the disability of finding social interaction difficult. And there's an awful lot of life beyond 40. I have a lot of friends who I can go to for support, and a lot of acquaintances who are always pleasant and seem pleased to see me - and only one (who I haven't seen since she emigrated 50 years ago) is from before I was 40.