Olivia
Not expert lah.. Just joking and adding some humour. Hee...
Anyway, re-looking at your timings, it is also possible you had a shorter LH surge this cycle coz you tested -ve on Mon afternoon, +ve on Tues morning and you probably O-ed on Tues since BBT shot up today. So even if the surge started by Mon night, to O by Tues (even at night), it would only be 24 hours. So maybe you want to test at other intervals rather than morning and afternoon. Maybe noon and night so as to cover more ground.
For Clearblue Digital Ovulation, you shouldn't use FMU. I just checked my instructions and it does say you can test any time of the day but as we all know, FMU should not be used as LH synthesizes in our body later in the day. Only for the Clearblue Fertility Monitor, you can use FMU.
Lynzi, pls correct if I am wrong