fetal doppler driving me crazy !!!

I can't find my baby's heartbeat on the fetal doppler and it's causing me tons of anxiety . I see these women who are finding their baby's heartbeat really easily at 8 or 9 weeks . I'm 12 weeks . I can only hear my own heartbeat on it 
Added info : I had an ultrasound 2 weeks ago and baby's heartbeat is great at 174 bpm. Everything is fine , I just really want to hear my baby's heartbeat at home !