Hey Taryn! Not sure I'm much help, but I agree with RumpledElf - after I stopped the pill, I found that there was really a particular time of the month that I was much more in the mood than any other time (when it's mostly just cos DH wants to, lol!). Also, having never used an OPK myself I have no advice there, but the creamy CM doesn't really equate to ovulation. I reckon I'd probably say actual O happened the day of or after those pains, then you get the EWCM to help the little fellas reach the eggie. Also, with your temps, a site like FF (not sure if you're using that) will pinpoint your ovulation after you've had 3 days of steady temp rises.

So, after all that rambling, if any of it makes sense, I'd probably put your O day around 20 or 21. I'm happy to be contradicted, but that's my take!