Why did my girlfriend dump me ? girl's please answer?

Well i was dating a girl i knew and we would go swimming and when summer ended and school started we weren't hanging out that much but we still talked on facebook and said i love you before we logged off and one day i went on my facebook and saw i had a message and it said i am breaking up with you i don't want to be in a relation ship no more and ever since than i have always still loved her and we were dating for about 2 months and i want her back and we are still good friends and whenever i ask why she broke up with me she will say i didn't want to be in a relation ship no more and recently i asked her if she would go out with me she sad i will think about it and after 1 day i asked her if she had thought about it and she said yes and she said that she likes someone else and they might date and i get a migraine whenever i picture her with someone else help