@suchaflair,
If the essay includes your name... and if he is trying to publicly embarrass you, then you might have a legal recourse.
If the essay is anonymous, or something he just wrote for himself, then he didn't do anything wrong. If the essay is something that he intended just for you, then it is a standard "I am angry" communication and you should just ignore it. There is nothing wrong with this either.
Bad relationships happen. People deal with it in different ways. Writing about bad relationships is not in itself a bad thing. And it is not creepy, it is a reasonable and healthy way to deal with difficult emotions.
If he is publicly embarrassing you then you should absolutely report it. If he is actually threatening or intimidating you then you should also report it.
If he is just writing for himself, or if he is writing anonymously about his feelings without mentioning you by name, or if he is just writing a last "I am angry" email then you should just ignore it and move on.