How do i make him want me back?

my boyfriend and i have been dating for three years and we know lately that we dont feel the chemistry like it used to be. as much as we both want it to work, we know it just cant. he also hasnt been nice to me like he used to be and i went onto his facebook and saw him having a conversation with one of his friends saying that he had "dibs" on one of the younger girls and that he could get her "easily". he also talked about how he thought me and him werent going to last much longer. i was so mad and upset that my friends helped me get up enough courage to call him and end it because we knew i had to do it before him. for the past week i have cried every night because i miss him so much but i can tell when he says he misses me too, he doesnt really mean it like i do. although i am sad, im also really mad at the same time. because i know as much as i do want to get back together....its best if we dont. i want to get him to want me back and regret destroying our relationship but i dont know how. i dont know if i should act like im sad and show him i mmiss it...or show him that im completely over it and am moved on wiht my life and other guys. i dont want to do this to win him back...i want to do it so he comes crawling back to and i can reject him and show him how it feels. i really need help and fast.