Negative ovulation test but still got pregnant

When I was using ovulation test back in March this is the darkest it got. I was sure I was out that month because it only got lighter. So I was super suprised to find out I was pregnant. Has anyone else still gotten pregnant with a negative ovulation test? Do you think this may have something to do with the reason I miscarried or was I just not testing properly? My pregnancy test were super dark after.