You don't need to go to school to learn to code. Especially frontend development can be learned with Youtube at home.

You know you are "good" at coding if you have experience and know that stakeholders could throw any challenge at you and you'd probably find a solution if it isn't out of scope.

But don't worry, especially in the first few years it will ALWAYS feel like you are the question asker surrounded by experts. This is not necessarily the truth but that's what it will feel like - don't let that take you down.

And, good luck!