Pregnant and due dates?

Ca

Hey all! I’m Caitlin and I’m from England!

On Saturday I did 3 pregnancy tests which were all positive!

My last period was on 8th December 2018

And my cycle lengths are normally 30 days.

I’m a little confused about working out how far along I am, on the nhs pregnancy <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">due date calculator</a> it has come up with 4 weeks pregnant.

My clear blue test said pregnant 1-2 weeks

I wanted to book in a private early pregnancy scan and I’ve booked up for the 9th of feb, they can view from 6 weeks?

How many weeks do you all think I am? So sorry I’m so new to this!!