Just thought I would reply (to me) to say I FINALLY got a positive OPK at 4.30 this afternoon. It is Day 19, so O will be maybe Day 20. I normally O Day 15. So if any other new-ivf'ers look this up it will hopefully be a useful reference for them. In my case, my cycle is approximately 5 days longer this month after my first (and hopefully only) IVF BFN.

Problem resolved