That feeling of not belonging/fitting in

I don't know whether it's because I'm not a pure autistic person, I also have severe mental illness, but I find it hard to fit in here. Others here seem to have no difficulty bonding with each other, and chatting like they've known each other for many years. That's a great social skill to have., but one I don't have. For want of a better phrase I'd say other posters  here are 'socially adept' in a way I'll never be. They lead far more high powered lives. 

They have/have had good careers . Have good academic qualifications. I never had a paid job, and only did a bit of voluntary work. My academic qualifications stopped at 6 O levels. I've never pursued further education due to bullying related trauma.  I have to have a lot of practical support because of poor adaptive functioning ability.