Relationship without love

I tell my girlfriend regularly that I love her. Really I'm only in love with images I distort of her in my mind. I change the way she looks constantly in my mind and I always find myself thinking about ways in which she is not pretty.
Also, her ways are too organized, and I find it difficult to avoid loathing her at times.
But if I stop the relationship I lose what was once one of my best friends, study pals and logical anchor to life.
I hate being an physically-focused person, but I am.