Bro, I feel your situation. As a matter of fact in a way i'm IN your situation right now. And I know it's hard to hear (hard for me to hear to) but trust me, she's moved on and so should you. What i've learned is that even in a great relationship, a girl should never be in control of your happiness. Once you give her that control, that power, your sunk.. because if she ever leaves you or betrays you, you lose your sense of self. You lose your self worth because you feel like without her, you're nobody, empty. I feel the exact same way. Just remember, you were you the individual before you met her.. and you are still you after she left you. Don't ever forget that. I'm sure there's nothing anybody can say to you that will make the pain go away, but believe this... The last person that will make it go away is the person who brought it upon you in the first place. Step one is cutting off all contact as horrible and as painful as it may seem. Talking to her will only make it worse. Do whatever it takes to avoid contacting her.
Be careful with your heart, because when someone seems too good to be true, they usually are.