unless you broke up with her, or it was because of some mistake you have made, all you can do is leave her alone and work on yourself.
I just saw and then talked to my old roomate who is now with back with her ex, guess what, he broke it off with her and she was still in love with him while going with her new boyfriend to thailand. When she came back her ex said he had been thinking a lot and wanted her back, she obliged and her now newly ex boyfriend freaked out, calling her friends, work, even her mom and talking sh!t about her and what not and guess what, she "lost all respect for him"
Women will date a man just because they dont have anything better. but thats a side note.
women will only want you back when you make no effort to get them back, or if you dumped them. those are your best chances.