I think I have social anxiety, and I would like help.

I just can't seem to talk to people. My parents keep pressuring me to find a girlfriend and go out and talk with people, but I just can't do it. Every time I'm in a social setting, I get nervous. I don't know who to talk to or what to talk about. I have a terrible time in social events, and the people I know are having fun with others. I can't do that. I'm really recluse. I just cant talk to people. I have this fear that I might say something stupid, and whenever I do try talking to someone, I keep replaying the conversation in my head and thinking about what the other person might have thought afterward, or what kind of impression I left. It's torturous. I can't talk to people without calculating the conversation and thinking about what the other person thinks for days. I can't even hold a normal conversation. I can't talk to people (unless they're really close to me), and it's really hard for me to meet new people. My parents keep pressuring me, and it doesn't help.

How can I treat this? Any help would be appreciated.