I'm freaking out my ex girlfriend is moving in with another guy.
Why do you think you will be freaking out?
Her next boyfriend will get all of my stuff
You should get your belongings back after a relationship ends. If you are too agitated you should seek professional help before you do something you might regret.
Fuck her!
Cursing her out will not get your stuff back. Just call her up and tell her to box your stuff and you will be there to pick it up.