<human>: Can you summarize the given text in a few sentences?

So I'm a student who arrived back earlier today to the room I share with my ex best-friend. It's the middle of the Christmas period but I had to come back early due to work commitments.

As soon as I got back I noticed some of my things weren't the way I left them. OK I thought he does that sometimes to fuck with me or if he uses something. Then I found a jumper/sweater that belonged to him on my study desk. OK that's kind of weird.

Being the OCD freak that I am I noticed my damn bed looked different from when I left it - the ornamental pillows weren't in their diamond formation (don't judge me). Then I noticed a bag I'd left on the bed full of junk wasn't on the bed but under my desk. Fuck.

I text my buddy asking him basically wtf had happened. He said quite openly that a boy and a girl had slept in it, so I may want to check the bed for 'juices'. At this point I'm furious. I'm so angry he:

A) Had sex with his disgusting girlfriend in my bed
B) Tried to cover it up.
C) Is showing no remorse.

I don't know how to feel. We have to share the room until the Summer, then I think I'm outta there. I told him in a raging fit I better hadn't see his face for a while or he can man the fuck up and say sorry to me...

A bit of context - he had text me a week ago asking if I would be back on Thursday just gone. I said no and assumed he wanted to check I wouldn't walk in on them since he knew I had plans to come back but I wasn't sure when. Imagine my surprise he was checking I wouldn't walk in on them fucking in my own bed....

I've got a taste for revenge. How can I get this bastard back/make his life as miserable as possible?
<bot>: My (ex) best-friend had sex with his girlfriend in my bed and is being a cunt about it. I want revenge and need ideas!