BFN and still was pregnant

Cassie • Momma of Two Graci 5-7-15 Graeson 9-7-16! Angel Momma of Two Nov 2015 and Twin B Jan 19 2016! Single Momma! TTC baby 3 via Sperm Donor! :) ❤️💜
How many of u had multiple BFN and was still pregnant but didnt find out till later??