sonoline b

I ordered the sonoline b fetal doppler to give me some reassurance. My first pregnancy ended in MC. Anyway with this baby  almost 10 weeks and haven't been able to find the heartbeat at home. I was told at my first appointment that the baby was "far back" can that make an impact on finding the hb myself? We heard a good strong beat 175 at 8 weeks and I'm just dying to hear it again. We go back at 12 weeks for a follow up.