good read for when the ex does contact you:
Q. I've been on NC for some time and my Ex just contacted me, what do I do?
A. The question is: Why are they contacting you?
If it's just to get something back, box up their stuff and have a friend give it to them.
Otherwise, there's no need to reply. No matter what, don't contact them back right away. Don't answer if they call. Show them you have a life and you don't need them in it. Yes, it's kind of a game but at this juncture, it's a necessary evil. I know a lot of people might disagree, but first of all, I would want to know why the ex is contacting me. If they are having doubts, they will make it clear. If you respond to them, be sure to take a day or two to do so. This will give you time to think clearly about what you want to say. When you reply, make sure that it's polite and to the point. Don't make any small talk. Don't bring up the past (big no-no). Don't volunteer any information about yourself. Be the first to end the conversation. Do be happy, do smile inside (CBT) and know that you'll be fine. Trust me, if your ex wants you back nothing will stop them from getting in touch with you. And this is ideally what you want. You want them to initiate the contact because it will be their heart that has changed.
If they really want you back, then you have to listen out for the apology. The complete 180.
"I'm really sorry for what I did. I don't know why I did it, but all I know, is that it was the most stupid thing I've ever done. I want to try again, and will do whatever it takes to make it up to you, prove I'm deadly serious, and regain your trust. Please, can you find it in your heart to try again?"
Anything other than this - any small talk, any "so how are you?"s, any tentative chit-chat - is just breadcrumbs. Mostly, to appease their own guilt, make them feel better, and confirm that they can still yank your chain.
The only thing you should actually ever respond to is a clear and absolutely unequivocal signal, from them that they desperately love you and would do anything to be able to try again.
Anything - ANYTHING AND EVERYTHING - else - is just a way of chatting with you and keeping you simmering on a back-boiler until you are roasted, broiled, cooked, done, shredded, dried out and falling off the bone.
Remember: The question is NEVER "Why are they doing *this* or why have they said *that*?
The question is always, but ALWAYS:
"What do I do now?"
And the answer to that, is to not try to head-read, or second-guess. It's to keep on doing what you're doing. Ignore it, and stay in NC.