Anyone have BFN 4 &5 days before AF, then BFP?

Jennifer

AF is due 10/8 and I tested on 10/3 and 10/4 and got BFN. I was cramping a few days after ovulating and they didn't feel like my normal PMS cramps, they felt different. My boobs are also sore. I don't want to keep retesting and getting BFN... but I want to know if it's common for early detection tests to be false negative.