Heartbeat.

I had an OB appointment at 11Weeks (exactly a week ago) Dr had a hard time finding heartbeat with the Doppler, she did an ultrasound & everything was perfect. Baby was just super active. I’m exactly 12Weeks today, I tried using my home Doppler && couldn’t find anything. I tried for 10Minutes. Should I be concerned??

*Ive found the babies heartbeat every time since 9Weeks.. (only used the Doppler about 4Times but never had a problem with finding it till now)