OPK'S testing

Christeen

Hey ladies.

Please see pics below.

Since December all of a sudden I have been late. I am currently ttc, last month I used OPK'S but I only had 10 so I am pretty sure I missed my ovulation date

I want to know when do I start testing my OPK'S this month.

I managed to get 30 OPK'S this month I dont want to waste, can anyone suggest when I must start testing