I'm guessing CD16. FF is probably just waiting for one more day of a sustained temp increase to give you crosshairs. But that is quite a chart, I've never seen a dip like that before. Are you temping at the same time every morning? Were you on any medications that may have effected your temp?
Oh, this is a tough one. What happens if you omit the 96.1 temp? Then it looks like you O'd on the 16th-ish. I'd be interested to see what the temperatures do for the next few days. Is it truely an upwards trend? Today is the first temp above the earlier ones. I'd keep trying for a few more days just to be safe. Is this your first chart in a while?