Thinking it's my AF but is it?

Graciela • Mom of a beautiful 3 year old girl and beautiful 19 month old son and now pregnant with baby #3!
Today I thought my AF had arrived and that had happened this morning and I barely filled half a pad. I also took a test this morning and it was a BFN. Has anyone had this happened to them before? I am pretty regular with my period and it being every 28-29 days. This has never happened to me before