Confused!!! Help!

Leslie
TTC #1, 19 DPO, AF was due 6 days ago, no symptoms of AF or pregnancy and 4 BFN.  I'm so confused, and although there are many factors for missing AF, I'm very discouraged.  Has anyone out there experienced the same or have any idea of what's going on.  Anything will help at this point!  I don't even know how to calculate my ovulation this month.