There's blood on my bed!?

I'm 14 years old ,and my sister's 26 and she also has a boyfriend. Her boyfriend can't pay his rent, so he's staying over at our house until he finds a job. So it's 10 o'clock and I'm going to my bedroom, but it was locked. And I can just hear my sister moaning. I knocked the door and wait for about 5 minutes, then they walked out of my room, pretende like nothing ever happen. Now my bed is covered in blood stains and sweat. What should I do about this? It was my bed! Ps. Sorry for the grammar.

Just tell them that it wasn't nice, not to do that again and to clean your bed for you. It's rude to use your room without asking and it's rude to leave it a mess afterwards.