If someone or the other were to break up with you, chances are that you would start feeling sorry for yourself. You should know that this is a symptom of low self esteem. People often break up with others simply because of the fact that they like the power trip that they can experience thanks to it. If you were to beg them to take you back, this would only give them even more vicious pleasure and they would bask in the glow of being wanted by someone that they are constantly refusing.
What you need to do here is to look into ways to increase interest from your ex girlfriend. The reason you behind this is that your ex likely broke up with you because she wanted to see what you would do and how you would react, and you never want to give her the satisfaction of knowing that you are hung up over her. If you want to make your ex want you back in a truly desperate way, the single best thing for you to do would be to get into a relationship with somebody else.
Suffice it to say that she won’t be able to stand the sight of you with someone other than her, and this would fill her with a jealous rage. Chances are that she would start calling you up and asking you to take her back, at which point the decision that needs to be made would be yours alone. You can choose to start the relationship back up again, or you can just call it quits and tell her that you are finally over her.