Hi, I went yesterday for my first ultrasound and I measured to be at 7 weeks 0 days with a heart rate of 91 bpm... my OB said it was lower than normal and we needed to follow up with another U/S next week. She also could not see the yolk sac which she said she was not too concerned with that b/c it could be hiding behind the baby. I am super nervous... I miscarried 3 years ago and would be heartbroken if this happened again! Has anyone had this situation?