I'm such a mess. I got my dream job but now I'm just hiding in the bathroom for hours.
Wait what? Why are you hiding in the bathroom?
I am so nervous.
It's understandable that you are nervous. However, staying in the bathroom might send the signal that you do no value your job. You should take a deep breath and fulfill your job responsibilities.
I'm not sure.
It's a new job and being nervous is normal but hiding like that isn;t showing anyone that you're capable of doing your job well. Even if you make mistakes you learn from them so buck up, take a deep breath and nail that job!