Hi, and welcome. Did you get the six weeks figure from an ultrasound? If so, you conceived about 4 weeks ago. Did you get it from a doctor who just asked you when the first day of your last period was but did not do an ultrasound? What he would have been giving you, if so, is the count from the first day of your last period. He would not have been intending to say that is when you conceived, though. Doctors (all medical personnel) use the first day of the last period to indicate the start of the pregnancy time period in weeks. They know you weren't pregnant then (you were having a period!) but they use it because it is a starting signal that everyone can see. Ovulation happens about two weeks later (on average) than the last period, but it is hidden and nobody knows when it happens for sure. So they add two weeks at the front end and use the period as a starting point for the count.