Slow heart beat (7 weeks)

I went to the ER and I ended up getting an ultrasound they said everything was normal my hcg,yolk sac,and everything else was normal and that I am measuring 7 weeks 1 day but than they said the babies heartbeat was too slow and that the heart beat was only 78 beats per minute the nurse told me not to worry that sometimes the heart isn’t found and that the heart rate is most likely mine and that’s it’s good that we saw a beating heart in the ultrasound but i feel like I should expect the worst has anyone ever went through this and I everything turned out okay