17 DPO - HPT negative yesterday and today

Yoly
AF late, should've come 05/09. Nausea, vomiting and diarrhea, headache, lightheaded. No spotting or cramps, no sign of AF which is weird. I usually cramp a lot and am right on time. Did any one else find out later than 17 DPO? Couple of friends suggested blood test, I'm
Thinking of retesting Friday if AF doesn't visit.