sound like twins?

Clare
I'm 17 weeks and at my regular appt the midwife said I measured big and then we heard kind of an echo while listening for the heartbeat (like maybe there was a second heartbeat just off sync with the first) only way to confirm is an ultrasound and she said there are other reasons to measure big so it's just wait for u/s now.
Did this happen to anyone else? I'm going crazy waiting for the u/s appt...
(Note- I know only the u/s will tell me for sure, just looking for similar stories or input from twin mommas...)