So I wake up to take my BBT reading every morning at the same time. I also use OPK. This month, my LH surge came abput 3 days later than expected. The LH tests are pretty obvious for me when the surge happens. So I know for sure that I had the LH surge on CD21. And then my BBT surge happened just as expected, and was taken at the same time, in the same manner as usual. DST happened on CD18, though... IDK if this had an effect. Anyway, so far the two days after the BBT surge, my temp has dropped back below the coverline. What could this mean?

For comparison, Jan-Feb vs Feb-Mar.