P.S can you do OPK at the same time as charting BBT? And if you can what days do you do them on and what time of day?
I do OPK and BBT charting. I use Clearblue Easy Fertility Monitor. It measures my estrogen levels along with LH surge so it gives me some warning of when I will be ovulating. I also test with regular strips in the afternoons (can't miss that ovulations lol).