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Hi, so I need help because I’m really confused!

So I have a cycle that’s from 27-28 days and started to take OPKs on the 9th day of my cycle and never once got a positive one. On cycle day 14,15,16 I have had ewcm and on cycle day 16 in the evening had spotting when I went to the loo and wiped. I’m guessing it’s ovulation spotting because I have been trying to read about it.

My question is because I never got a pos opk when shall I count 1DPO? Shall I do it from cycle day 17 because of the spotting on cycle day 16 and ewcm? Please help and reply, much appreciated.