First time hearing heartbeat

I'm all sorts of nervous this week. My appt to hear the heartbeat is Thursday, and while I know everything is probably fine I can't help but fear they won't be able to find it. Everything got thrown off because I was having pains at 7 weeks so they did my dating ultrasound then instead of 9 weeks. Baby looked great and on the ultrasound the  heart rate was a strong 169...but I'm still scared. If they can't hear the heartbeat, will they send me for an ultrasound same day to make sure baby is ok? Our next one wouldn't be for 2 1/2 more weeks and that's a long time to wonder if things are ok if they can't find it!