You broke up with this guy when you were only 14. First love is a powerful thing. I’m sure your feelings were genuine. I’m sure you experienced the relationship as the most important thing in your life. But you were only 14.
What you needed then is not what you need now at 16. No matter how charming and interesting the guy is, your lives have evolved in different directions. You are both now more mature and becoming the adults you will be.
I suspect your problem is not the break up. It is more likely that you continue to think about this guy because you are insecure about meeting someone new. Instead of getting back into the social life of your school, you withdraw into thoughts of an old and very young romance.
The way to move on is to look forward instead of looking back. What are you doing now to make more friends and to be more socially confident? Are you actively involved in school activities like a sport or club? Are you volunteering at a place where other teens are working on a project together? Doing these kinds of things is a low pressure way to get to know other teens without the pressure of worrying about dating. Friendships often grow naturally into something more.
I wish you well,