On Letrozole and trying IUI's.. missing ovulation!

Normally opk's work for me. I ovulate regularly, normally day 12-16. Lately while trying to catch it right before I ovulate to try IUI, I go for the ultrasound today (CD12) and I've already ovulated! Blood work will confirm that later today.

So frustrating! That means I likely ovulated before day 12 which is abnormally early for me. This is the second time I've missed my ovulation.

Is it time to give up hope of trying another IUI (one attempt with no success) and move in to IVF?

Help!