If they pressure yout to go out to concerts, the shopping centre etc. then they probably aren't worth having as friends anyway. If you don't like social situations then just don't get involved in them. It's hardly something to worry about, you prefer to be alone. So do most people on the autism spectrum.
Enjoy life the way you want to, not the way others want you to.
Besides, NT's get high of social situations, it's like drugs for them. We don't.