want my ex back from a time ago, shes taken, what do i do!??!??

okay, ill try to keep it short, we dated 5 years ago for 2.5 months, broke up, had sex rarely off and on for 2. we talked about getting back together a half a year ago, i told her i wasnt ready. she pressured me into it. then i soon broke up with her 2 weeks later (i wasnt ready). during the 2 years we were apart for a short time was in a relationship with a foreigner. I told her all he wanted was to marry her and get citizenship, she broke up wtih him, and it turned out true at the time. 6 months ago, when we broke up, she got back with him, hes married (she knows) and lives 1000 miles away, she says shes happy, i told her i wanted her back and that the last time i wasnt ready, she doesnt believe what i say b/c i said the same things last time to get her not to marry the guy (shitty i know, but its all i could do cuz i didnt want her hurt) but she hasnt said anything like "we are done", "there is no chance", or anyting pointing out we are getting back together, she says shes "happy" but the ironic thing is now, i want to spend the rest of my life with her in all the true senses. i cant sleep at night, i think about her all the time, and i want her back and ill do anything

what do i do?
what do i say?
please help

and btw i am 24 she is 21

sorry, tried to make it short so people would read it, she is with the married guy and she says she is happy with him. she says she doesnt believe me when i say i want to be with her and that i miss her, cuz i said it once before and she thinks i lied cuz i broke up with her after we got back together the last time. what do i do with that?

he is only married for citizenship, i dont know why, i hope its just b/c she cant be alone and its simple for her, i know i want her. i have talked to her plenty, told her plenty of what i want. i dont know why she wont tell me a definitive answer, when i ask if its over between us she jsut says somethin weird like, "im happy"

i have tried to meet many others, i only want her, i cant stop thinking of her, i have seen her, she will not see me anymore, she says it is not fair to her boyfriend

Then the solution is simple. Write to her one last time about how you felt she is the one for you. How serious you are and that you will wait for her. Then after that, move on and get on with your life and don't look back, stop all contacts with her. If it is meant to be, she will one day contact you. But if she doesn't, you did not waste your life away waiting for her. It's that simple. Why continue to torment yourself. One of these days you'll meet another girl that will make you forget this one. It's hard to believe that now, but you will.