Scared

My ultrasound isnt until Dec 2nd and Im so scared there wont be a heart beat.   I went from symptoms to just about no symptoms and with the stress in my life and my sister having a miscarriage at 12 weeks, its scary.  She went in and no heart beat.  What are the chances of that happening to me too? Part of me doesnt even want to know but Dec is a long time right now.  :,(