So I haven't been taking these consistently so I don't really know how they work. The box said don't read after 5 minutes, but it also said you can keep them and compare with different days. I checked it after 10 minutes, and the lines are similar....is that a false positive to ovulation? Can I trust this one? Or does it need to be read at 5 minutes and anything darker after is wacky? Please help! Thanks! ?