My advice - don’t be defeatist. There’s plenty of time to meet someone.
If you get nervous in social situations, try taking up a hobby to socialise. It’ll give you something to talk about with others, and it’ll let you meet lots of people.
You may want to consider why you push others away when they get close. If you can figure out why, you’ll be able to work on it. If you’re really struggling, I would advise a counselor. They may also be able to help you with your low self esteem.
Above all, just don’t worry. Relax, enjoy yourself. And don’t settle because you think you’re too fussy or because you don’t want to be alone - take the time to find someone who complements you.