Am I depressed? If so, what should I do?

I feel like a failure, a mere shadow of my former self. I have frequent suicidal thoughts, I wear all black, I am sadistic (do NOT call it emo, very different.), People at my school call me goth, I listen to screamo, death metal, horror metal, etc. I love horror movies/books, but not like paranormal activity, more like Nightmare on Elm Street, Children of the Corn, etc. Edgar Allen Poe is my favorite poet. When we wrote poems in language arts, mine all included death, suicide, and sadistic qualities. My room is painted black with Dark green in the corners, and is adorned With murderdolls, slipknot, black label society, etc. posters. I am tormented beyond belief at my school, and I have been in fights, I usually win because I barely feel pain, So when they hit me it drives me more.There are basically only three things keeping me from killing myself. Also, I am a Harry Potter fanatic, but I like the Death Eaters, Slytherin is my favourite house, and I always wanted Voldemort to kill Harry. So I just want to know, am I depressed? Should I seek help? Because as of right now I keep my feelings bottled up