How can i win my ex back? ?

i have this guy that all through 6th grade liked me and i rejected him. so in 7th we went out for 2 months. then he broke up with me and now that i have gotton to kow him i REALLLLLLLY like him. no one knows i do. just that i miss him. lol so i talk to him alot and we hang out and i flirt but he likes my friend who DOESNT like him at all. how can i win him back!?