Hi this my help:
https://www.babycentre.co.uk/a561822/how-to-use-ovulation-predictor-kits#section3
"The kits can measure LH, but since LH can surge with or without the release of an egg, they can't indicate whether you have definitely ovulated after a positive response. What's more, false LH surges can take place before the real one. Most importantly, you should never use these kits as a contraceptive, since you can still become pregnant for about 24 hours after ovulation."*
I know from a doctor I used to have that O can happen more than once in the month. And this can depend on the emotions too.
I had a positive test this month but I am still not convinced that we got the right moment.
Good luck!!!