It doesn't sound as embarasing as walking in on you and the next time same thing happening his parents walking in, in his place.

YDI, and you should consider how much worse the outcome could have been than an awkward talk.

This is where you pretend you don't speak English. I know it's your parents, so you'll have to convince them that some sort of Freaky Friday thing happened to you and the girl you switched with doesn't speak English... ...and is a big ****!

How old are you? Are you living in their house? Depending on these circumstances, YDI. And if they're able to hear you having sex, I'm guessing you all share a house. So either you're too young to be having sex or you have no respect. If you own the house and they're staying with you, well, yeah that sucks but they don't have to stay.