boyfriend did a cheating prank on me 2nd UPDATE

My boyfriend did this terrible prank on me last week. I came home from work and him and his best friends, girlfriend acted like they were having sex in our bed. And his best friend was hiding in the living room to watch out for me to give them the signal that I was coming in. So I came home went into my bedroom and she's on top of him in some lingerie similar to something that I have and I thought what she was wearing was mine. When I "caught" them he says "you weren't supposed to find out like this!" While she acts scared and kept saying "sorry please don't tell my boyfriend". I walk out the room quietly and I go get a bat and I started swinging it and I told them to get the fuck out and I didn't mean out the door I wanted them bitches to jump out the fuckin window half dressed and we live on the second floor.