Not to imply you're not ready, but in response to "I've been coding since I was young, so I'm not worried about struggling academically":

"Computer science is no more about computers than astronomy is about telescopes."

Depending on the nature of what your department offers, be prepared to learn about, spend time on and potentially struggle with concepts that have nothing to do with coding or software engineering as you might be familiar with it, or even sitting in front of a computer.