[Always *]

Well, what's done is done. Has your dad said anything about it? If not, maybe he won't. It might be to awkward of a conversation for him to be like "yo, child of mine, why are you having sex in my bed?" He might just take the approach that A) it's too awkward to discuss and B) at least your using protection and C) wash the damn sheets and shut it from his mind.

If he does bring it up, I would just apologize for having had sex in his room, promise not to do it again, and just grit your teeth through the conversation.

Obviously, what happened is embarrassing, I would definitely feel the same, but honestly, you dad is probably just as uncomfortable (for different reasons though). I would just get through is and hope for the best, it'll pass in time.