I dumped my girlfriend for a silly reason & i want her back but she doesn't want me back even tho she loves me?

i dumped my 9 month girlfriend 4 changing her gcse option from geography to childcare as i had told her a week before that if she changed it to that i would dump her, so that she wouldnt change it because shse doesnt even get a gcse from it, but just a certificate and i wanted whats best for her && so i thought a gcse in geography would be better because i had all A* coursework, but anyway... she told me the other day that she had changed it to that so i said to her " you know what i said id do if you done that" && she just told me 2 f**off && walked in (home). she left me some texts sayin f**k you && stuff like that && wouldnt answer her phone, so i went off in a temper && smashed up my fone && went inside a derleict house && punched walls && cut all my hands and face open && then i saw sense && went home && cleaned myself up and asked to meet her. we met && then we seemed to talk fine && i helped her with her paper round && she was jumping on me && hugging me telling me how much she loved me && kissing && i thought everything was fine. BUT..... when we had finished the paper round && went in i signed in on msn && on her msn name it read....iloveyouusam - my husband to be !! x (this isnt me btw) && she insisted that he was just a good friend at school && wasnt her type. she then followed on to say that she didnt want to get back with me because she said she cant handle it where i go off && cut myself in a temper smashing things up. she later comes round mine && i help her with her homework && then we were fine && as she left she had left her phone behind && i found a new text from sam saying... beth i love you !!! im not wiv mina any more && im now biking home, i wish i could be with you tho !. i questioned her immediatly about this && she looked confused && surprised. she then text him sayin wtf sam, wat was that all about? && then insisted that she had to leave && when i said beth im confused whats goin on she said, i dont want to talk about it. later on msn she still insisted that she had no feelings for him watsoever && is still saying that she doesnt want to get back with me, but yet shes saying that she still loves me, but just wants to be alone and doesnt want a boyfriend right now. shes really heavy on her period at the moment && i dont know if thats got something to do with it but i really do hope that it does. im so confused && i really dont know what to do as i really do love her more than anything in the world. shes the only thing i have right now as ive been permanetly excluded from school and me && my parents are constantly argueing. ive been with other girls before && never have i felt the same way about them as i have with beth. please help me. what can i do or say to her to get her back?