Confused AF

Alright ladies. I have been going back and forth with these strips and the apps.

My apps keep switching Ovulation date every time I scan a test on to the app.

The strips seem consistently dark the past few day’s and I can’t seem to notice a difference.

The last one (21) is today’s test.

The (19) looked dark to me so I could have sworn I was close to ovulating than.

Now I’m confused because of today’s test.

Help please.

I’m new to these strips so I’m not sure if I have to switch brands or keep using these.