have you ever heard that Grateful Dead song with the line that says something like when you left how was I supposed to know what you really meant was please don't let me go?
Don't worry. You're ex is totally into you. It's just a matter of time, patience and proving yourself to her to build the trust back up. THink about it. You put her through 2 years of back and forth. Maybe it will take at least one year for her to stop saying that she's not getting back together with you.
I would wait a few more months and then if she says it again, just tell her that you understand and you respect her decision, but to please not keep mentioning it because it hurts since you are extremely sorry about what you did, regret leaving her and wish that you could still be together.