Spotting or slow start to af....?

I’m 13dpo with average cycles of 37 days, today is day 36 and I O’d around day 22 (going by opk not bbt). I’ve been feeling some af like cramps and last night noticed some pinkish but only when I wipe. I’ve put a pad on the last few hours but nothing on it as of yet. Af usually hits hard and heavy, but isn’t it too late to have implantation spotting? Tested yesterday morning bfn. Anyone had something similar?