Doppler tips?

Myia

I'm 10 weeks today! I had an US at 7 weeks 6 days with a heartbeat of 161! I have a hand held doppler that I want to use to hear it myself but I'm struggling! I have the sweetiesong pocket doppler. It keeps popping up a hb number between 130-150 but I dont hear anything. Its started to freak me out a little and I'm getting in my head. What should i do!?