Two heartbeats?

I know this sounds completely crazy but I am finding two heartbeats, about two inches apart with my Doppler at home. I know what a heartbeat sounds like as this isn't my first pregnancy or baby and I've been finding the baby in ONE spot for the past 4 weeks. I've only had one ultrasound at 8 weeks 3 days (baby was measuring 5 days behind so 7 weeks 5 days) and it was only one. However I'm an identical twin and my mom didn't find out about us until 5 months (24 almost 25 years ago granted). Anyone else have this kind of experience and end up seeing a twin on the next ultrasound? I'm 13 weeks 2 days, and I'll be 16 weeks for my next ultrasound.