There is absolutely nothing wrong with you. You are 18 years old.

Your life is just starting. Wanting to be single at your age is a totally normal feeling. And there is nothing wrong with breaking up with your BF if that is what you want. You don’t have to stay with him just because he makes you happy, or he is a nice guy. Both of those things can be true, but it doesn’t mean you need to stay if you don’t want to.