What do I do to win my ex back

Why did you lose her?

You need to provide more information please.

From personal experience, you can't win an ex back. The most you can do is let her know how you feel and the rest is up to her.

https://www.askmehelpdesk.com/relationships/how-get-him-her-back-187766.html

Agreed. Trying to "win" an ex back is a waste of time and effort and will only lead to more frustration. You didn't provide any specifics about your particular situation but just by the way you worded your question I think I can safely say that you need to just pick yourself up and move on.

This isn't a game. You don't play to win.

If she wants you back, she will come to you. If she doesn't, then accept her wishes and move on.