Roommate sex etiquette?

I sleep over at my guy's house pretty often, anywhere from one to four nights a week. He has three (male) housemates, and one of them has a room upstairs right next to my fella's. The other two reside downstairs. We're in college.

I am always completely embarrassed to have sex when his housemates/company are present. Sometimes their friends stay over late (until 1am on a weeknight). Initially I avoided it but that kind of led to no sex ever, except those rare mornings when we have the house to ourselves. We will usually put on some music and try to be generally quiet, but it's not always easy!

And I think one of the worst moments is, after we've just done it, trying to shuffle sneakily to the bathroom (clothed!) and running into a roommate. I think my face turns bright red and I wonder if I'm grossing them out with my obvious sex hair. Or if they've heard us. THEY KNOW!

So what are the basic rules of etiquette when getting it on in the midst of your SO's roommates? Or how to not be so obvious about it? Should we wait until everyone is asleep?