doppler picking up no heartbeat

Leanne • Married & pregnant with baby Andrews #4
I'm 9wks & 6 days & i still can't find babys heartbeat with doppler?? Has anyone else had this problem?? it will be my 5th baby 9th pregnancy after mc still getting all symptoms ect of been pregnant I'm quite worried i had a scan at 8 weeks & bby was fine with a good heartbeat