I think it's over....

My girlfriend and I have been talking and she says she has alot on her mind, she says she's happy but I don't know...... I talked to her best friend and she told me that my girlfriend met somone els, I don't know what to do I was thinking about talking to her about it she and I never had that problem before. I feel sick thinking about it..... Iv'e been with her for about a month and really felt like she is the one for me but I guess she dosnt feel the same.......