im 13 and just broken up with first love help!

[rob missing rosie]

right, well im only 13, and i have had so many girlfriends, but all of those girls have just been fun, and then i met a girl on msn, and i talked to her all the time, turned out she was in the same year, and sam school as me! and lived very close to me! As we talked more, i fell for her more. And then one day i asked her to come to the pictures with me. So on July 19 2005, we went and i asked her out, and she sed yes! That was the best time of my life! Things started off perfectly, i was in a realtionship with a beautiful girl, who wanted a serious relationship, and would never do anything to hurt me. The first few months were amazing, and when we first properly kissed, magic surrounded me, and that was when i belive i fell in love with this girl. I felt so happy, and since then i walked around head up high, like no one could get me down, because the love was holding me right up there, above everyone else. I had more confidence in myself, my behaviour in school was so much better, i didn't get any detentions while i was with Rosie. (i used to get one a day). But then all of a sudden she started to change, she wore more makeup and dressed with more revieling clothes. One day she went to town with her friends, and met me afterwards, then her mates went off and it was just me and her alone. She got a text, and said it was from a boy, she got his number before me and her got together, but then when i got home, i looked on one of my girl mates msn spaces, and it said that on that day, Rosie got a number off 'a well fit boy' I knew Rosie had lied to me! I confronted her, and she said, well i want to act my age, and since then things got worse, and she wanted to act her age more, and go out and flirt and kiss other boys! I couldn't belive it, so 5 months after we got together, we broke up. That was 3 weeks ago. She says she loves me, but she just wants to act her age, but she does love me. But yesterday, she kissed my best mate! behind my back, and said she didn't. But she then told me the truth, and i dunno what to do, i just want her back in my life, becasue i do love her i really think i do, so how can i get her back in my arms, where she belongs. I want the magic to suround me again. Since we broke up, i have been excluded from school and i get in so many fights, because my confidence has gone, and shes the only person who can brong it back! I jus want her back in my life for good!! What should I do? I cry every night, and try to hold it in all day. I think of her 24/7. And im always upset now. please help!