The doctor is telling me that from the ultrasound I am 5 weeks pregnent. My LMP was on September 14, 2007 I ovulated around the 28th and had sex on that night only. I had an ultrasound done on Nov. 3rd, and the doctor said that from what he sees, I'm only 5 weeks pregnant. How can this be? My LMP was 7 weeks ago, and weeks in pregnancy is dated back to your LMP. So shouldn't I be 7 weeks pregnant and not 5? And if I am really 7 weeks, then is the baby developing slowly because there is no heartbeat, just a yolk sac?