I graduated from high school in (gulp) 1984. I have traveled many roads since then. I didn't start undergrad until 1998.
You will be fine. Lots of folks take their time getting ready for college. It is an important time of preparation. Making sure you are ready for the work in college is what you need to do in order to be successful in your studies.
Now it is time for you to hit the books and study your butt off. Good luck. Work as hard as you can, BUT remember to take time off to enjoy the things you enjoy outside of academics. Otherwise you will get burned out.
All my best,
Amy