I also fall into a couple of different disorder's also. But I am 100 percent sure that it is because of trauma I have suffered throughout my life and they begin with Complex PTSD.

Like you I can be very social also. But only as long as it is with people I know and am comfortable with.
I never initiate contact with anyone. No matter how long I have known them. I except almost all invitations, but I never extend them.
I will go to someone's home, but I will never invite anyone to my own.
There are no exceptions. Siblings and my adult children are treated the same.

The reason is always the same. The fear of rejection. And I will always reject someone first if I think for one minute they are going to reject me.

So, no clear label. I am just glad that I know where it comes from.