Anxiety.

I really fear for my future. I am so far behind in everything that sometimes I just want to give up. I'm still young. But I overthink the smallest things. I can't order food, meet up with people, or even get a job without my heart pounding out of my chest. I want a job and a car so badly, yet won't because of how nervous I get. This is how my brain works. Okay, I want a job. So most people just go fill out the application and such with no problem. No, not me. I think "where do I go for the application, who do I ask? What door do I go into? How do I ask exactly. What if I mess up and get too nervous to show back up?" Etc... I've been like this for a very long time. When I was 15 I used to never leave my house, I wouldn't even go into Walmart and rarely out to eat wth family. Because of fear of saying something wrong, or being judged. I want a car too but I don't understand the basics that everyone else does. How do you do this or do that. How does insurance work. How often do you do this or that. Before someone calls me stupid, believe me I know these are normal life things just everyone knows. But it messes with me everyday, and I never get these thoughts out if my head. I fear even getting married when I'm older because I don't know how everytbing works. My mind is constantly thinking this and that. Nonstop. It's killing me. I feel so alone with all of this confusion on top of everything else. I just want it to be easy like it is for everyone else. It's normal life things that I find so difficult and my heart pounds. This overthinking and anxiety is preventing me from what I want to do and taking over my life.. I don't know what to do anymore. Any advice?