Heart rate

So I’m 11 weeks today and for a week now I’ve been trying to find the baby’s heart beat and heart rate with a doppler I bought and I’m having no luck.. I picked up two different paced heart beats today, not different by much. I added the beats per minute and for one got 76 and for the other got 104 per minute. I’m starting to get worried. I haven’t had an ultrasound since 6 weeks and we seen the heart beat then but didn’t hear it. If I did find my baby’s heart beat and it was only 104, what does that mean?? If it’s not the baby’s what was it ???