Two heartbeats (not mine) on Doppler??

Tanja
I'm a bit nervous ...a few nights ago we were doing the Doppler at home and picked up the babies heart beat on my right side then as my boyfriend slid the Doppler to the left we also picked it up on my left side. (Quite a ways away from where it was on the right. And no it wasn't my heart beat. It was another fast swishing one!😳 has anyone had this happen? I've had 3 ultrasounds and I'm almost 14 wks now. Is here anyway they could have missed a twin?