Home Doppler- 15 weeks - and I just found 2 heartbeats?!

Christine
So far for all my ultrasounds and other Doppler experience there has only been 1 heart beat... but today I heard 2! One to the slight left and the other way right... I have an ultrasound later today but I'm kinda weirded out that I heard 2... anyone else ever experience this?!
Edit - I know the difference between my heartbeat and baby's. Mine is slow and swishy and baby's sound like a train.