Calculating due date from OPK

[Random49]

Hi all, I’ve recently found out I’m pregnancy with my first baby but am having trouble working out my due date.

I’ve always had irregular cycles which are all over the place, my most recent two being 41 days and then 71 days. My most recent cycle started on 20/12 and my first positive OPK was 14/01. I’m obviously not 6 weeks pregnant but every calculator online only seems interested in the last period date!

Does anyone know how to work out due date based on ovulation? I had my first positive OPK and some pain on 14th and then another positive on 15th.

My calculation says either 7th or 8th October but I’m curious what others think!

Back 2 weeks from your positive OPK and put that into the calculator as the first day of your last period - very irregular too from 50-101 days so i known the frustration, got me an early scan from the nhs though

If you don’t mind me asking, did you get the scan early because of irregular periods?

Your actual due date will be around 2nd October. Yes they will normally scan you based on LMP date, my experience has been they don't trust a date based on OPK's and/or would rather err on the side of caution so as not to miss the window to get accurate measurements at the 12 week scan so you would be given a due date based on your cycle, go for a 12 week scan when you're only 8/9 weeks and they'll rebook your for when they expect you to be 12 weeks.

@Random49 yes I did, I went to the drs after a positive test and when they asked my last period it was 5months prior, and I said I'm obviously not 5months but have no idea how far I am so they booked me a scan as soon as just incase