Home Doppler

I ordered this angel sounds home fetal Doppler and I'm having trouble finding the heartbeat. What I thought was the heartbeat was just the placenta swooshing... Did anyone else have this problem and everything end up being ok? I'm 11w4d. My last ultrasound was 11/11 and the baby was measuring 9 weeks and heart rate was 168 and then last Monday 11/17 the dr got the heartbeat of 170 with her Doppler. I haven't had any bleeding or any discharge at that. I should've never ordered it bc now I'm a nervous wreck. I have an appointment on 12/2.