How to get over your ex boyfriend?

So over the summer for three weeks me and this guy from my school dated we never really talked in school we just met from a mutal friend and started datin i am 16 and he is 15 i was his first gf and i really liked him and care about him. It has been almost a month since we broken up and i have been heartbroken and sad i dont feel the same anymore. This is why i dont usually date guys in my school because i have to see him everyday and he talks to some of my friends. What should i do to feel happy again and move on?