Stressed, upset and confused

Teisha
Officially 3 days late for af, tested my 1st late day, and got a bfn. I know bodies change but my cycle and cycle signs have been pretty consistent for the last couple years. I know when it's coming, and it's always on time. Know no pd, mild cramps, slight nausea for a week, mild lower back pain for over a week, fatigued every day for 2 weeks. Any ideas?