Fetal heart rate with personal Doppler

Ok so I have been crazy paranoid and anxious during this pregnancy since experiencing a missed miscarriage last December . I purchased a fetal heart rate Doppler about $100 one, so lastnight I had an ultra sound and baby looked awesome kicking and moving its arms, putting thumb in mouth, I am 14 weeks and the heart rate was 156 lastnight , I also had another ultra sound a week ago and the heart rate was 155. I get home lastnight to discover my Doppler in the mail I got it out and I'm pretty sure it was the heartbeat and it was reading between 80-100???? My husband counted along with it and it was correct ??? Not sure if I was wrong in thinking it was the babies heart beat , anyone else with any experience like this ????