Hi all. I'm new to this!

I have been using the OPK strip tests and always getting negatives. It says that results come up within 1 min - 10 mins and that after 30 mins results are invalid. So I have only been taking the results under 30 mins and ignoring the rest, although I have seen the strip having positive looking results after 30 mins.

But now I'm confused as I have seen some pictures where people are keeping the sticks, but surely those results are invalid? Or have I been ignoring correct results?

Please help 🙏😩