I feel this way from time to time, I assume it comes from being self-taught and not always knowing what my peers know. Meditating helps, as does having a supportive SO.
I, too, am self-taught. I spend a decent amount of time in terror, imagining a sea of unknown-unknowns just waiting to ruin my projects or make me look the fool.
Try to let it be a source of motivation, rather than insomnia. And don't worry, after a few years, all that extra work trying to keep up with imaginary peers really adds up.
I'm self-taught too, your comment really resonated with me. I'm a contractor so I'm always having to try and figure out what "level" my peers are at. Once I start to get to know people though I start to realise that they usually have the same self-doubting attitude as I occasionally do.
It's not just self-taught people. Many professors, who have gone through the full range of degrees from bachelor's to master's to phd's, also suffer from this. (And grad students, who are proto-professors.)
I feel this way from time to time, I assume it comes from being self-taught and not always knowing what my peers know. Meditating helps, as does having a supportive SO.