Will anything concrete change in your life
will you get kicked out of your home, will you suddenly be financially responsible for things you previously weren't, etc.?
If it's any consolation, a lot of us don't feel like adults, and that's ok! My kids seem to think I'm a grown up, so I managed to fool them at least.
Just keep learning as you go, and ask questions. We all love talking about things we know/have experience with (just ask the average Lemmy user what Linux distro you should install...), and there's basically no such thing as "cheating" when it comes to figuring out how to be an adult.
One day at a time!