Twins?

I had an vaginal u/s at 8 weeks 3 days and there was only one baby but I have an at home heart Doppler and I've heard 2 heartbeats not including my own about 2 inches apart and one is about 10 beats faster than the other. Could it be an echo or could they have missed a second baby. I've felt like there was twins and the more I think about it the more I want it. The picture is from my first u/s