Tmi about urine ....

Hello , I’m struggling a bit to test ovulation with opk , I’m used to using opk’s for years now with no problem , it’s just due to be being on a diet and drinking a lot .... my question is .... when is the best time to take a opk test ? I have been taking one with 2nd morning urine ( so it’s obviously still strong ) but I’m starting to wonder if it’s giving me a false reading due to my urine being strong it says im high then at night i take one and it’s gone down a lot ! I’ve had to take all of my morning urine test strips out of this photo as there was a massive difference morning to night ...

I also can’t test in the afternoon or tea time due to me drinking so much in the day due to loosing weight (2L/3L a day ) and i physically can’t keep it in for 4 hours to test !

Any advice anyone for a accurate test ? I have tried temping but it’s just not for me ! Thankyou 💕