If the 1st Dr gave you an u/s pic of the baby and said everything was fine, then I would guess that it was just an unclear pic. on the second one. Was it a vaginal u/s b/c you are so early it can be very difficult for them to see via an abdominal u/s. I wouldn't worry, just wait 'till next apointment and I'm sure you'll get some good pic's and probably see the heartbeat.