Period 7 days late. Several BFN

Michele
What is going on here? I am 7 days late and keep getting BFN's. I have been using this app to track my periods for the last 11 months and each one has been regular and always comes on time.
I don't necessarily think I feel pregnant. I'm a little tired but no other symptoms of pregnancy. 
Anyone else experience this before? What was your outcome? Pregnant or did your period finally come?