Hi G8r4evr -- As you can tell from my earlier posts, I am not a fan of OPKs nor BBT'ing
, but here's what I learnt along the way...
My first ultrasound was part of routine health screening package that included many things incl. reproductive health -- at that time Gynae saw the u/s image and said "ok, so you've O'd"... I looked at the image and she pointed out the dark circular shape of the egg (or "follicle" as she called it) in the uterus.
My second ultrasound was not really planned, but when I went back to my Gynae for routine Pap test, I casually mentioned that its been a few months TTC'ing and nothing happened yet, and she remarked "ok, do you want me to take a look and confirm whether you O'd"... and since I don't bbt or use OPKs I agreed. Again, she confirmed O and showed me the same dark circular shape in the uterus that she called Follicle.
Apparently, you can't tell at that stage whether that is a fertilized egg or not, because it is too small to tell whether fertilized... so it apparently looks very similar to a pregnant u/s of about 3.5 weeks (I believe you can only see yolk sac inside that dark circular shape in pregnancy at about 5+ weeks).
Is that the only way to confirm O? --- According to my gynae "seeing is believing"... so she feels that that is the only 100% foolproof way to confirm that you O'd in that cycle. BBT is a good way to indicate whether O happened -- but she said it was not 100% (highly accurate but not foolproof, as temps can be high due to other reasons etc.).
From what I've learned from the other ladies on this board, OPKs are not that reliable at all -- and may not work in everyone...
CM is a good way... but again, can be thinner/runny etc. again also due to non-O reasons.
Sorry for the long post! -- but hope you find at least some info that helps you.