12 days late.. late ovulation ? Bfp

Sarah

I was 12 days late before I got a positive pregnancy test. Would you still go off you last period to calculate how far along you are? This was my first cycle not on the pill, so I think I know when I ovulated(I can almost always tell)and it wouldn’t be in the window all of my apps are saying. I’m truly clueless if I am 6 weeks or 4 weeks..