You had been a challenge for her. You had a very high appeal and she was irresistibly attracted to you. Now she's gone and you are saying: "I want my ex back!"
I'm preparing to make a wild guess here, but can it be that as time went on, you grew to become less and less of a challenge for her? And can it be that at this time, you're zero challenge for her? And that she knows if she wanted to, at any moment she could get you back again and twisted around her finger simply by saying the word?
I'm going to be a bit crude here, however as you may already know, to become a challenge again you must demonstrate to your ex that her sexuality has no control over you any longer. Take into account what it's like when you're stalking her with not returned phone calls, voice mails, text messages, and emails. And after that think about just what it's like when you keep on doing it (as a lot of guys do) even after she's told you to stop. You're suggesting to the woman that you are a low-value guy without any other dating alternatives.
Your lover is not going to respect you again until you refuse her sexual influence over you. Luckily you're doing that now by not personally corresponding with her. The last thing she needs to hear from you now is how much "I want my ex back", so stay away from her.
You should definitely stay 100% strict with your communication cut-off. Don't be "friends" with her, simply because that rewards your ex with the continued approval of power over you while giving her a convenient excuse to stay split up. (She reasons that she's letting you down easy doing this, assuaging any guilt she may experience.)
On the other hand, make sure to keep her locked in with your stuff. Probably quite a few your possessions are at her residence, and vice versa. She may also owe you money as well. She may ask a mutual friend of yours to ask you if you'd like everything returned.
The ideal response to this is "No, not yet. The justification is because her holding onto your things (and you possessing hers) is still locking the two of you in and guaranteeing future communication. You do NOT want to provide her the psychological closure that would result from settling your accounts.
For the next three weeks, you must fully recognize -- and embrace -- the undeniable fact that you're an independent guy now. Take what happened with your ex-lover and learn from it. You have a great chance to transform your life which will eventually allow you to get your exgirlfriend back.