Why am I cutting and sad ?

Well Im sad and happy. I cut myself , not deep but with like a broken mirror part or a shaver thing, it fells good. Iv thought of how to kill myself , I know Ill never do it though so I don't even try but I still think of it. I feel sad on the inside. I was sad and I didn't talk but everyone else did, about me so Im acting happy again. I just dont know what to do, or whats wrong with me. Im parnoyed too , and I live in a nice house not many family problems, but my parents fight a lot. Whats wrong with me.. ://