Another sac??

I had my first ultrasound today, measured 5+5 and got to see a heartbeat!! There was another smaller sac that was seen, however it was too little to see if there was anything in it or not. Has anyone had a super early scan and seen one baby, then gone back for another scan and seen a twin??! I’ve had this nagging feeling for awhile that I’m going to have twins. So I’m just curious!