Should I worry...

So we opted to get an elective early gender ultrasound through my OBGYN office. So the staff was trained and went to school and had degrees for their job. Which made me feel the ultrasound would be more accurate. Just a personal opinion. It’s another girl!!. Anyway she let us listen to the heartbeat and she was smiling and talking with us. Then we heard a really odd sounding, more quiet couple beats of the heart and she frowned and shut the sound off instantly. She said nothing when I asked her about it and just asked when I was seeing my doctor next. She tried to act all bubbly like she had before but it came across way more forced. She also rushed the rest of the ultrasound before typing on the computer in my file for a long time before letting us leave. We have been freaking out since that something might be wrong with our daughter. My next appointment with my doctor is on the 10th but I can’t help but worry.