I have the same problem. I avoid people and seek out somebody to teach me how to do things better, but haven't found anybody yet. The problem might be social cues, and Theory of Mind, and so on.
For example, we have 1.5 seconds to recognize somebody and acknowledge them - otherwise they think we snubbed them. That's easy for NTs, difficult for Asperger's, and impossible for people with face-blindness like me. And the rage is wild! I saw it when my boss didn't recognize a co-worker at a baseball game - he looked straight at her face for a few seconds, then looked away. She was beside herself with anger - I think she's thinking of quitting. And yet, he did exactly what I do - try to figure out if I know somebody and guess wrong.
It's hard for an adult to get a teacher for social cues - although I don't know why we shouldn't just learn in the same class as the small children - it's the same thing to learn. Anyway - people have suggested acting classes and Toastmasters. They are possibles but I haven't tried them yet. I was very impressed by how "mainstream" my brother became with Toastmasters - it's optional, he's not mainstream unless he thinks the occasion calls for it. But he learned the mannerisms of one who "belongs" - it might be worth a shot.
Personally, I've decided that "mental health groups" are not for me - I don't have a mental health problem, I have a social cues problem; I'm not likely to learn good social cue response from those groups.
All the very best of good luck to you - don't give up - no effort is wasted.