Still confused about how far along I am!

N

Ugh. I’ve posted about this before but I still don’t get it. Can you help?

First day of last period January 9

IUI January 25

EDD from online October 18

Based on date of last period I would be 4w5d. Based on IUI I’m 2w3d (which I know I don’t go by), but with EDD of October 18, that’s 40w2d?!

Why can’t my brain wrap around this!!