Hello Y: Yes, I understand completely the desire... the need... to be alone. I spend as much time alone as possible. I've never seemed to get along with people. Just as you say, I've often wondered if I give off some vibe that turns people off. It used to bother me when I was young. However, as I've grown older, I've come to value my aloneness. I'm married & I love my wife. But even with her, there's only so much togetherness I can tolerate.
My one social outlet is the internet. And I enjoy being on-line. But the same people I correspond with on-line I would probably not want to be with IRL. And I suspect we probably wouldn't get along well anyway.
I don't know why some people end up being hermits. (I often refer to myself as an "urban hermit".) But that is the direction in which my life has taken me. And I'm content it has turned out that way.