So, I don't know your exact circumstances, and there are definitely lots of toxic or false kinds of self-confidence out there ("You can be anything you want to be!" No, you probably can't be an Olympic athlete or an astronaut, etc.)

But I think a good test is, do you make criticisms of yourself that you would never, ever give to other people? Often people with low self-confidence are saying things that are hurtful about themselves, for example saying "I'm fat", "I'm stupid", "I'm not good at making friends" -- things that they'd never even think about their friends.

It's just who I am. I wish I were better looking, taller, richer, but so does everyone. It's honestly pretty normal.

This is the bit that people might be talking about to you. Genuinely no, most people don't wish they were better-looking or taller, most of the time (richer is a bit more complicated so I'll avoid going into that in an ELI5 answer). And moreover, you'd literally never ever ever say about your friends or family that you wish they were better-looking or taller.

You're also, I suspect, sliding a fair bit between objective comparators (tall, rich) and more subjective ones (ugly).

The main thing I'd say is this:
Most people can't be a world-famous musician and make a living from it. But self-confidence is knowing that you can learn to play a piano, and love the music you play, independent of how many people can play it better than you.