How exciting!! I decided to keep going after high school and am getting my Masters now. Let me tell you, this is one of the best decisions you will ever make! Good luck to you and let me know if I can be of any help! Don't worry about being nervous, I get nervous even now on the first day of class, you just don't know what to expect! But you'll be fine!
Do you know what you want to go into? Go with your strengths and what you enjoy. I loved math/numbers so it was natural for me to go into engineering. You can pick whatever you want, just make sure its something you can see yourself doing for the rest of your life
Good luck to you and keep us updated!