My fraternity brother is acting weird because we messed around. Advice?

I'm 19 and belong to a college fraternity. I consider myself straight, but one night after a long party with a lot of drinking, I ended up having sex with one of my fraternity brothers. I've never really been sexually attracted to guys....and this just happened out of the blue. I'm fine with what happened, it's really no big deal to me and I'm not ashamed. I still like girls and I think of this as an interesting experience. My frat brother is playing the "I was so drunk", I don't remember or 'gay drunk' card in public. We both get teased about it from the other frat guys. Now, whenever we're in the same room, he acts like he doesn't know me....I can see he's uncomfortable being around me. Privately, he made me promise to say nothing happened....but the truth is everybody knows and it would go away if he didn't keep insisting nothing happened. He's a good guy and I like him as a friend, but I don't know what to do. I'm comfortable for myself just saying, "yeah...it happened. we were drunk"...next subject, because I don't really care about the labels and I do think the other guys in the fraternity are also cool with it. I mean, it was just sex and I'm not asking him to be my bf or gay marry me. Any advice? Do I need to carry his shame and lie or should I just tell the truth. I'd like talk with him privately, but he avoids me like the plague. What I'd say is dude, it's no big deal...I don't really care if you're straight or gay and one experience of sex with a guy doesn't mean you're gay or "turn" you gay. I had a few experiences with some guy when I was like 15, just masturbating together and some oral stuff, but no anal sex. I didn't think that made me gay because I had a girlfriend from 16 to 18 until I went to college. I am sorry for such a long question...i'm struggling with the right thing to do, so I guess I have 2 questions really? Have other guys who identify as straight now had sexual experiences with other guys growing up and how did you deal with that and what do I do. I want my friend back; I want him to feel comfortable but I hate carrying a lie that doesn't need to be carried. I'm not ashamed and the fools who want to slap a label on me so they think they can then "understand" who I am can go right ahead; I could care less. And again, I am real sorry about how long this is.