I do not know why but ever since my grandma died I have not been me. HELP?

In 2008 my grandma died and something changed in me. It was the harshest thing that had ever happened to me and to this day I remember the exact day she died and what happened and also her funeral. It seems they are stuck in my head. Shortly after that I became angry, I was becoming aggressive and even some of my friends were afraid I would hurt them. I would cry and feel sadness but I would never be happy. I seem to have crushes on almost every guy that is good looking even though before I would only concentrate on the personality and wouldn't care about the looks. My friends keep asking me one question "why are you so mean" and I reply with "I wish I knew I truly do" The only thing I truly know and care about is my gorgeous cat he is my only link at the moment with the real world. Everyone of my friends do not understand me and criticise me about my choices but I always seem to choose the wrong choices. Even becoming friends to some of my friends was a bad choice. I cannot seem to do anything right. I need help finding myself and I really don't want to go to a psychiatrist or a doctor. I have tried to turn back to what I was before but it is to hard for me to achieve. Please if you have anything that will help let me know. Please no silly answers.