You were a challenge for her. You had a superior appeal and she was irresistibly drawn to you. Now she's gone and you are saying: "I want my ex back!"
I am about to make a wild guess here, however could it be that as time went on, you started to be less and less of a challenge for her? And is it that now, you're zero challenge for her? And that she understands that if she wanted to, at any moment she could easily get you back again and twisted around her little finger just by saying the word?
I'm going to be crude here, however as you may already know, to develop into a challenge once more you need to demonstrate to your ex-girlfriend that her sexuality does not have any influence 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. After which think of just what it is like when you keep on doing it (as quite a few guys do) even after she's told you to stop. You are suggesting to the woman that you are a low-value guy with no other dating choices.
Your lover will not respect you again until you reject her lovemaking power over you. Luckily you are doing that now by not specifically communicating 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.
Make sure you stay 100% strict with your communication cut-off. Don't be "friends" with her, simply because that rewards your ex with the continued validation of power over you while supplying her a handy excuse to stay split up. (She reasons that she is letting you down easy that way, assuaging virtually any culpability she may feel.)
Then again, always keep her locked in with the help of your things. More than likely lots of your possessions are at her residence, and vice versa. She may also owe you money as well. She might request a mutual friend of yours to ask you if you want everything back again.
The ideal response to this is definitely "No, not yet. The rationale is simply because her holding onto your stuff (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 be caused by settling your accounts.
For the up coming three weeks, you have to totally accept -- and embrace -- the fact that you are an independent man now. Take what occurred with your ex and learn from it. You have a wonderful chance to transform your life which will eventually allow you to get your exgirlfriend back.