I am so confused!

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AF 8 days late. Lots of cramping (like period cramps), achy, exhausted, and generally feel sick. Pregnancy tests are negative. Did an ovulation test out of curiosity (brand new test), which showed peak ovulation. This would mean I ovulated 36 days after my last period?? I took OPKs beginning October 8-24, and all showed high, never a peak. Anyone else experience anything like this?