I can't believe I cheated in a teachers restroom.
That sounds strange. So what exactly happened?
I don't want to talk about it, just leave me alone
It sounds like you might be feeling a little guilty. It is wrong to cheat afterall, let me know when you are ready to talk about it.
I just wanted to try cheating but now it doesn't feel good
It probably does not feel good because cheating is wrong. You are deceiving somebody and the person will feel betrayed.