Heartbeats

Am

I'm 10 weeks pregnant today. I have a doppler that my sons grandma got me for fun when I was pregnant with him. Yesterday afternoon I found a baby heart beat on my left side. Last night I found one on my right. Were those 2 separate heartbeats or could one of my twins switched sides completely. They are in their own sacs. So im just wondering if I heard one baby or 2?