Im due October 18th, 13 weeks tomorrow and i conceived near the near the end of january...
Your ultrasound is adding in the 2 weeks extra. Even though you had only been pregnant for 5 weeks they are adding the 2 weeks and saying 7 weeks.
Sperm can also survive for a week, and implantation takes 7-14 days. Honestly, you would do best to save yourself the headache. (this is usually why doctors say to wait till you have a period before you try to get pregnant, lol) Unless paternity is called into question when you got pregnant does really matter.
but i only had sex on 17th 18th jan thats why i am confused lol i wish i could go off myLMP but never had one not had one since last year
I think you've really confused yourself. It's not only your midwife that adds two weeks. All doctors do. When an ultrasound is done those two weeks are already done and added in before it happens. The reason this is is for a 28 day cycle. A girl will ovulate (generally) on day 14 and then implantation occurs around 2 weeks later. This places you at 4 weeks pregnant. Like the others said, you don't count from the days you had sex or from conception. You count from LMP or more often ultrasound. I agree with the others. Based on your due date you conceived sometime from January 28th-February 5th.