ttc mummies, i just got pregnant on my last cycle and was using clearblue ovulation test kits, read some queries here about the use of it so would like to share my experience and of course, baby dust to all of you !
based on regular cycle of 28 days, doctor said will ovulate between D14-D16. so I started testing using first morning urine on clearblue on D14. D14 -ve, D15 -ve and D16 +ve. And then nurse say this means i will ovulate either on D16 night or D17 morning, within 24 hours of the LH surge. Before this, dr said hb to empty on D13 or D14 so as to ensure by the time need to release, will have freshly produced sperms.
Eggs take 3 days to travel from the ovary to the womb and sperms lifespan is 2-5 days. So in this case can do it on D16,D18 and D20 (if sperm is long life type, will still be able to catch the egg in time).
The above is an example to illustrate how the kit works.