A nother Love in a twist

As I look into her eyes and tell her that I love her I see someone else that I want to be with. I have had a crush on her for years, and every time were near I find my self more and more drawn to her. And I mean I dont want to end the relationship that I have now. But I want the relationship that I have longed for for years almost since I layed my eyes apon her perfect body. And when I say I love you to the girl I am with now I find it to have a lesser meaning than what it once had before. And I dont know what to do, should I leave who I am with now or go for the one I have been longing for, for years and who I know better. I am lost with out someone by my side, and it kills me to keep this secret from the girl that I am with now but for her sake, I have to or she will be crushed for a long time. But my girlfriend is so obsesive and it is driving me insane and it kills me to be in, this much pain again.