What the hell am I?

I am Cameron a girl with a death sentence. My end is about to come. Then I decided that I will do one last daring act before the curtains close on me. I decided to go cliff jumping. On the way I witnessed an accident. The man in the car asked me to take a metal briefcase. He begged me to destroy it. He made me swear that I would destroy it. I took it home before mom came back. I left it in the fridge thinking that I will destroy it in the morning. The next morning mom comes to my room with the vials. To my surprise she used them thinking it was part my meds. It miraculous cured me. I never imagined that my nightmare had just began. I have this crazy thirst that shows up out of nowhere or the urge to beat someone. I had better learn how to control these urges and stay hidden or I will lose all those I love.