What to do about my bi friend I'm falling for

I'm not, personally, a fan of big emotional revelations unless someone is in a relationship. And you kind of aren't. So! Instead, change that.

How?

By asking him out. On a date. Tell him - let's go get coffee/a drink/see a flick/grab dinner - I dunno, whatever you like. Look nice and make it clear it's a date. And see what happens. But you need to flip this script and push your interactions with him away from only being about sex.

He may not want to go along with your script flipping, but it's worth a shot.

I have to ask, is he in he closet when it comes to his sexual prefs? Do other people in his "bubble" know about your friendship with him? I hope that you are not a 'dirty little secret' in any fashion, but I would do a few things to test the waters before I gave up on him.
Ask him out on a date, movie and a dinner, something that a couple would do and see what response you get.

If he refuses a date, then it would be obvious that all you are to him is sex. If that's the case, as hard as it would be, you need to move on. Why keep breaking your own heart in hopes of him suddenly wanting a relationship with you instead of a friends-with-benefits situation?

In any case, I wish you nothing but the best, and I commend you for not falling into that stereotype that all gay men want nothing but sex as it is clear you want a relationship. If he isn't willing to go down that path with you, remember there are other fish in the sea that are looking for the same thing you desire. Yes, it may be heartbreaking to let go of the possibilities with your friend, but in the long run, it may be a good decision for you to let it go and find what you seek in someone else that seeks the same.

Good luck, and remember, take care of yourself first.