Impossible though it seems, you can give it a try. It actually depends on how long you have been with her. Certainly, if you are missing her that bad, you have been with her for a long time. That is one point that could work in your favor. Over the months of your relationship, she must have developed some strong feelings for you. That could help you in winning her back.

Remember that it is after all her choice. She is entitled to decide who she eventually wants to be with. All you can do is to make her feel that you still care and feel deeply for her. But you should not cross the line at any point. One wrong move and you could lose her forever.

Do you know the man she's going out with? If not, try to find more. What is she getting with that man that you did not give? This could be anything, from a very considerate companionship to good sex. If you can find out about that, you will be in a better position personally. But remember; do not open out these issues when you confront her. That could be devastating.

Okay, now you are equipped with the right kind of information. Now you have to make your move. Muster your courage and communicate with her. Call her up. If she has walked out of her own will, she will take the call. If you fought with her and removed her, you will have to try harder now. When she begins talking with you, speak of casual things. Do not become mushy right at the start. Just speak as a friend. Ask her how her life is going. She might hang up, she might not. Either way, you will get an indication of whether she's happy with the way things are happening or not.

Most probably, she'll ask you how you are doing. This is your cue. Tell her you would like a date with her again. Her answer will tell you how difficult the situation is. But you have to do this. Or else, you will never be able to find out whether she still cares for you or not. In most cases, the girl might be waiting for you to call, or might just be teasing you with the other man. When you take the first step like this, you will know what the right position is.

It is going to be very, very difficult. No one can tell you how to get your sweetheart come back in your arms forever when she is dating someone else. But you have to make the effort. And in all this, you have to make completely sure you are not being unjust or unfair to the other chap. If things work out your way, all three of you must sort everything out.