I was experiencing pregnancy symptoms for a couple of weeks but wasn't sure if I was going to start my period or if I could be pregnant.  But went to be one night and woke up in the middle of the night covered in blood, like extremely bad, heavy period but never experience it to that extreme.  I and the bed was just covered in blood, it was horrifying.  Got up and had to take a shower, and bled after that like a normal period for a couple more days.  Not sure if it was a misscarriage or an extremley heavy start to my period which I have never experienced since.  This happend about 3 years ago in my late 30's.