My LMP was 26/10. So I am currently 4w 5d since LMP. Just went to doc for blood test this morning (hcg 1310) and he advised that dates are calculated from ovulation and not LMP so I am only about 3 weeks. He has asked me to book a 6 week scan but I am confused about why he calculates different from everything I've ever read. Do I book my scan based on LMP or estimated ovulation?