The answer is simple: You're just not attracted to him. Attraction is not a choice. What you feel for him is probably AFFECTION, and not ATTRACTION. There is a difference - affection can grow and be nutured, and can start even after years of hatred for one person. Attraction on the other hand, is something that can't be controlled - it usually can only be automatically triggered by a greater power.
I know a lot of girls that stay with their jackoff boyfriends. I ask them, "Why don't you just leave the motherfucker?" and they just go, "I dunno, I just want to work it out." They're attracted to something about the guy that drives her crazy, and it overpowers all the other negative things she doesn't like about him.
And trust me guys, if you try to be the knight in shining armor to these poor girls in situations like this, you just fall into the friend zone. :evil: Then they say things to you like, "Aw, you're such a nice guy." But that doesn't mean they'll go out with you. :evil: