Sure, why not? You can DOR any day you please. At the Academies, however, DOR is a multi-week process involving every link in the Chain of Command all the way up to the Superintendant, with suggested stops at the Chaplain's office as well. However, once you have hit each chain of command and heard them out, it's still your choice 100%.
In NROTC, I've read here that you can DOR on the spot, and the next day you are no longer part of the Unit. I also imagine you need to discuss this with your NROTC Freshman Advisor, plus whoever he/she reports to, and then finally the Professor of Naval Science in charge of your Unit. They may be able to help, they may not, but remember you are making a decision that will affect the rest of your life, so don't do it rashly.
If you are a Scholarship cadet, you had better have the conversation with your parents about how you will, or they will, or you both will pay for college without the scholarship, book $, or stipend $.
P.S. Search threads here from kids who have DOR and then later realized it was an ill considered, emotional, or illogical decision that they regret often. And there is no going back. Then there are those who DOR'd and to this day are glad they did. Don't search on "DOR"... that is a phrase not used that often. Search on "quitting", "withdrawing", etc.