Hi, Im 10 Weeks Pregnant And Yesterday Had My First

Hi, Im 10 weeks pregnant and yesterday had my first ultrasound, My usual doctor is on vacation and the replacement doctor waesnt used to the old ultrasound machine, I had 3 Sacs and he went over to one sac that was empty and then went over to the one on the left which had my baby, he never went over to the bottom one, What im wondering is why do I have 3 sacs? and I took a video of baby and something pops up can you tell me if thats another baby ?