If you are asking why your boyfriend stopped talking to you, don't feel that you are alone. This has been a question women have asked since Adam and Eve. Things can seem to be going along smoothly in your relationship and suddenly your man disappears. If you do manage to get him on the phone, he will give you some lame excuse like being so busy at work or having to help out his family or a friend.
If you really care about him, you will want to believe his story, but if he loved you he would find a way to make time to see you. There is a reason for your guy acting this way and by understanding how his mind works you can get your ex boyfriend back. Think of what was happening in your relationship shortly before he disappeared. You can't consider anything too small because men are more fickle than you may think.
By being fickle, I mean that your ex might have been offended by something you said or did that you thought nothing about. For instance, you he might have considered you pushy or needy if you were sending too many text messages or making too many phone calls. He could get the idea that you are either dominating him or leaning on him too much. If you have talked about the future too much, he might have thought you wanted a commitment and run before you could trap him.
Then there is the fact that he could have caught you in a lie or that you slept with him too soon. These are the bigger things that might have turned him off, but if you were rude or a little testy about something, it might have been what triggered his flight. You need to know what caused him to want to get away from you before you can begin to patch things up.
When you think you have things figured out, you may have the urge to call your ex boyfriend and try to explain your actions, but he will either not take your call or he will make some excuse to cut it short. Which means that your best bet is sending a text or email. Make it simple and just say that you have some things that you think he should know and invite him to have lunch or coffee. This could make him curious and he will agree to meet you.
Since this might be your only chance of getting him back, you don't want to blow it by crying or begging him to forgive you. In fact you shouldn't mention the problem at all. Treat him the same way you would treat an old friend. Find out what has been happening to him and bring him up to date on your life. Do not be romantic and try to make him laugh. If he likes what he sees and doesn't feel any pressure, he should want to start dating you again.