Yep, that's PTSD alright. My advice:

1) Go to a psychiatrist who doesn't have a long wait list. This person will give you medication for your social anxiety, along with practical life advice. They don't "pretend to care", they just do their job like any other person. If you go to the ice cream parlor, the kid gives you an ice cream and kind of cares, in the sense that he would feel bad if the ice cream killed you, and he would like for his customers to be happy. Similarly, the psychiatrist is just helping you out and performing a service.

2) After you get your medication and some advice, start to purposefully approach certain people with the mind of making some friends. In this way, you will see who you are in relation to those around you, and you will form a sense of self.

As an aside, I have been feeling like a stowaway on planet Earth for about 35 years now. I currently have absolutely no local friends outside of my neighbor, my "at-work" friends (i.e., potential backstabbers), and my boyfriend. It's too much freaking effort for me to make and keep friends, especially when I always feel like they're judging me. However, I have found that my feelings of alienation decrease by a lot when I have a few friends. I am being lazy about it, but that's no excuse for you to be like me.

I know it seems like there is no hope, but there is a glimmer of hope inside yourself. You just have to see it. And if you have to walk the Earth three times over to find one person who can see it too, then you'll be in great shape so it's fine.