Bittertruth is right, you have to get divorce first. And about youe ex not helping you, there should be some legal way. Especially when you guys have been separated for so long, lawyers should be able to find some way out. Incase you don't, just go to your ex and ask her to get you divorce coz she is married too and i am pretty sure she wants to get it over with too. Its great that you guys have moved on and time heals everything.
And if everything fails, you just got to prove that she is married and moved on.