Can someone please tell me what happened to me?

I was living a happy normal life until my aunt, who was in remission, died suddenly of a brain tumor. I found myself deeply saddened by this but I barley even knew her! Then things started to change in school (middle school is already hard enough). I found myself distancing from my friends and I became very conscious about what other people thought of me. I became paranoid and somehow lost my sunny, easygoing, kind, fun, personality and my drive for life. I'm overwhelmed by sadness now and the fact that I can't connect to other people anymore. I want to tell my parents so badly, but I how can I when I don't even know what happened? Can a professional please tell me what happened to me? Is it a depression? I can't keep whatever it is a secret much longer because it's killing me.