I had my first Dr.'s appt. on 2/27/07. They did a pelvic and an ultrasound, which my dh and I got to see the sac. The Dr. said everything looks good so far. He estimated me at 6-7 weeks and due date of Oct 17th. How come we were not able to see hear the heartbeat? I know the books say usually at 9 weeks you can hear the heartbeat. This is my first pregnancy so not sure if this is normal or not. Any advice?