If you really do have feeling for her, do something sweet. For example: come to her house one night with chocolate and flowers. Say: I miss you and want you back. I'm sorry if I upset you in any way but you mean the world to me. I know we can work out any problems that are going on between us. Honestly, I've never felt this way for a girl before. Without you, I feel empty. Please, I love you. | That is what a girl wants to hear. She may be cheating on you so be prepared. This is coming from a girl so I can see where your coming from. Good luck! :)