How do I know

I did this test yesterday and this morning, yesterday second line appeared slightly darker then this morning, im finding it hard to understand the lines as your most likely at peak when they are super dark... I have 2 tracking apps and even with the same cycle data they both have different ovulation dates by 4 days in between. So im finding it hard to know exactly when I peak. I did notice the egg white discharge yesterday which was a day after sex yet not a day I was predicted to ovulate but tested and both lines came up....