Negative test, now positive?

I’m 2 weeks late. I took a test at 1 day late and it was negative...then I took a test around 5/6 days late, also negative. Today, at 16 days late I took one and it was a very bold positive. How does this even make sense!? I have 3 other children and tested positive BEFORE my missed period with each of them. I’m so confused! Anyone else test positive for the first time at two weeks late?