Still confused about how far along I am!

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

First day of last period January 9

<a href="https://glowing.com/glow-fertility-program">IUI</a> January 25

EDD from online October 18

Based on date of last period I would be 4w5d. Based on <a href="https://glowing.com/glow-fertility-program">IUI</a> 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!!