15 Weeks so frustrated

So I'm 15 weeks today and we just had a huge blizzard.  I was supposed to have an appointment this morning and it was cancelled.  I have yet to even hear my baby's heartbeat.  They tried at 11 weeks and it was too early :(
Now they rescheduled for a week from today.   I just want to know that everything is ok.  The wait is killing me.  I'm not showing yet at all and I don't have any symptoms anymore so I'm scared that I'm having a missed miscarriage.
I had the first trimester screening done 3 weeks ago and heard nothing back so that's good right?  I'm sure that would detect if something is wrong?
I just want some answers.  I see all of these people at 15 weeks having had 3 or 4 untraaounds already and I still haven't even heard my babies heartbeat on a doppler.  Another week of waiting is going to be hell.