<human>: Could you distill the essence of the text into 1-3 sentences?

Living in a small town in the Midwestern states I have known these two girls for my entire childhood. Growing up with them I have always had a major crush on my girlfriend (who we will call Amy), with it only coming to fruition senior year. Amy is quite literally the girl of my dreams, the relationship is going swimmingly well even though we go to two different colleges this year. We make time for each other and have excellent communication. Making sure eachother's needs are met and we both are very happy together. The sex is nothing short of incredible to boot.  

All through those horrible hormons filled years however I regularly masturbated to a specific fantasy involving a threesome between Amy, her good friend Chloe, and I. I always had interest in Chloe as well, but never really wanted or pursued a relationship with her, just simple sexual gratification (that never came). 

Anyway, after starting to date Amy I continued to use that specific fantasy as a sure fire way of getting the blood pumping when I'm on my own. The past year however I have sometimes thought about only Chloe when I am on my own, something about the wrongness of the situation makes it all the more sexually gratifying. 

Chloe goes to the same college as I do, and is staying in the same building a few floors below me. I see her on an almost daily basis, and often encounter her when I'm high and or drunk. Other people that hang around us have noticed and commented to me that Chloe looks at me with "those eyes", and I notice it as well. I'm quite sure that if I gave in to the temptation she would readily go along with it and that terrifies me. 

I really don't want to fuck my relationship with Amy up over something as dumb as sexual gratification. If I cheated on her I am aware I would never be able to forgive myself and it would be disastrous for our relationship. 

So reddit, how do I fix my lustful brain in order to stop drooling over my girlfriend's friend?
<bot>: I can't stop thinking of my girlfriend's friend as some type of sexual object and am scared it will lead to disaster.