You've changed

I realized I was turning into a monster when I noticed that I was chewing up the inside of my cheeks.  Spitting out my dinner, I ran into the bathroom and opened my mouth.  There were sharp little points poking out of my gums, just underneath my teeth.  Touching one of my teeth caused it to move and then come loose and fall onto my tongue.  When I pulled out the tooth I noticed my hand, the hairs on my hand were getting thicker and my nails were coming off, the skin underneath black.  I looked into the mirror to see a Halloween mask staring back.  Screaming and stumbling out of the bathroom scared my wife and kid, they then became terrified at seeing the horror crawling toward them.  Their running tweaked some internal instinct to chase, tear, and eat.