IUI-Confused about how far along I am?

I did an iui on November 30th and got my bfp from that procedure. I know that most women don't know their exact conception date so the typical practice is to go off the first day of your lmp, which for me was Nov 20. I've calculated my due date both ways (somewhere between Aug 22-Sept 4) but am unsure how to use this app. According to the "your baby is this size" factoids, should I be looking at the info for a 4w6d pregnancy or a 2w6d? I've looked at both and the 2 week one just seems behind of where I thought it would be. A few days ago it was talking about implantation, for example, which I thought would be earlier. Does this make any sense? lol Help!