Feelings for Best Friend?

So, I think that I might be falling for one of my closest friends, only months before he is moving away.

I have this really good friend that have been in my life since I was a sophomore in high school ( I am a senior in college.) We have been really close and at times practically inseparable, we lived right near one another and saw each other about every day for over a year. Things have been very platonic between us over the years, and we are so close that at times the idea of seeing him in a romantic way is weird. I have also been in a relationship for over 3 years. There have been these moments where I will feel an attraction to him, and maybe sometimes him to me too. Usually these are fleeting moments.
Lately I have been having lingering feelings and even fantasies about him and I, mostly sexual. We still hang out very often, my boyfriend is ok with this but sometimes will have a bout of jealousy, which had until recently been unfounded. Nothing has happened, and I have no idea that he'd be feeling this way about me. He has a girlfriend, of a couple months in out social circle. Since we are seniors and so are our significant others, things are kind of at a crossroads, he is moving far away so he will be breaking up with his girlfriend, and my boyfriend and will be moving out of our apartment and it might mean a break for us too. but not before he leaves. I'm sort of confused by my feelings. I have such an urge to have that experience together, at least once. It's a mean temptation. But, i am not that person and nothing will probably ever happen.

If someone could respond I would greatly appreciate it. I have put this up on another blog and no one wants to help. I can't talk to anyone in my life about it because of it's sensitive nature, i'm going to bust!