Hey WBAM,
I temp'd too when I was on BCP and it actually said I "O'd" on day 21! News to me...
It just goes to show that even accurate temping can make FF see the wrong thing. My advice? Temp anyway, it allows you to learn the normal temp ranges of your body, the differences of waking up at different times, different weather, and also allows you more focus on CM and other things (you still get that while on BCP). Therefore when you actually DO TTC, you will know what the difference is, and will be able to monitor the "real" signs of O rather than the ones in your head.

Good luck.