First off... I have no proper mental health training what-so-ever, so take anything I say with a grain of salt. But I do have some experience.
It sounds like you were raised in a more difficult situation than I was, but I did suffer some of the symptoms you have, and probably still do to some degree. I was raised by my mom. Dad bailed and didn't want to have anything to do with me. On top of that, my mom probably shouldn't have ever had a kid. She wasn't very good at it.
I was incredibly shy as a kid, and well into being an adult. That's not too abnormal, but it usually wears off for most people by the time they get to about mid grade school. It didn't wear off for me. As I went up through to high school, I found it harder and harder to interact with people, until it got to be impossible. I had a hard time doing the most simple things, like just talking to a stranger or even buying something at a store. I would have pains in my stomach in the morning when I had to go to school, or do anything more than just hang around the house. I did have some friends, but managed to alienate most of them. I also had an incident where two guys basically tried to abduct me when I was about 12, which didn't help things. I eventually dropped out of school because of all this.
This fear of things and people has lasted to some extent, but it's worn off quite a bit. As mentioned, you should try and get therapy. I wish I had a long time ago, because I think it's definitely made my life a lot more difficult without it.
One thing I did that I do think helped a lot... We eventually moved to a different city... a much larger city. At first, that just made me more afraid. But what ended up happening was, I got a job as a courier. It was very difficult at first because I knew nothing about the city. But what it did was help me learn how to do things on my own. I drove around by myself all day, so I didn't have to interact with people constantly. But when I did, it was for very short amounts of time. I had to do all sorts of things like file papers at courts, go into all sorts of businesses and different places... The cool thing was, nobody ever really cared to talk to me that much, so it slowly allowed me to just kind of get used to doing all sorts of different things by myself. For some reason, when I was doing those things as a job, it gave me more courage than if I had been doing them for myself. Maybe there was something about being in a larger city too. We came from a town where everybody knew you, so it was very hard to feel like somebody wasn't watching you. In a large city, there's so many people that you just feel like another one of them... Nobody knows you.
To this day, I still have problems with things like that though. But in some ways, not nearly as much as other people. I have to do jury duty downtown next week, which I still dread, but at least I know how to get downtown and where to go... and that's more than a lot of people.
It just takes baby steps... Go to the park, go to church, just go for walks... Simply getting out and seeing the world little by little helps. Things you first dread you may be surprised to find you actually like after trying them. I know it's hard, but try not to assume people are always thinking about you. Because most of the time, they aren't... trust me. Most people are so self absorbed, about the only think they think about is themselves. There may come a time in your life when you actually wish people were thinking about you.