Sounds like we're both very similar in regards to anxiety in social situations. I wish I had a magic solution for you, but unfortunately I don't. The best thing to do is to actively put yourself in social situations that make you feel like crawling under a rock. Go to various clubs and live events. Just dance at first, maybe occasionally saying a word or two into local chat. If you keep this up, just being there, then HOPEFULLY you'll get more comfortable being around others. Once you feel yourself feeling less awkward and anxious, you can start chatting more. Complimenting the song choice, asking everyone how their days are going and so on. What also might help is joining a community on SL that revolves around your interests. There are plenty of groups who have sims in-world for like-minded people to gather and chat.
No idea if any of this helps, I know how it feels when people suggest things you've heard a million times before, but just wanted to throw my ideas out there.
Wishing you all the best!