So I have one calendar that says I ovulate on the 17th another on the 18th and glow says the 20th

The opk tests that I've been trying to use for some reason haven't been working or showing results so i dont know what I've been doing wrong since I used them before and got them recently so I guess faulty batch ( equate ones )

So I'm not exactly sure when I could have ovulated but I've been having sex every day for the last two weeks lol

Any advice and recommendations for better opk tests