How does it work? I am on cd42 as I didn't ovulate till 6 days ago checking a <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">due date calculator</a> tells me I'm 6 weeks pregnant (I'm not pregnant yet) but if I catch this month will I finally find out a true date on an ultrasound around 12 weeks (England) which might push me back 2 weeks?