Trigger shot but OPK says low

Nikki

Sooo... finished my clomid 100mg for 5 days .. on Monday the 2nd my doctor said everything looks good so i took my trigger shot in the office. I took a OPK on Tuesday & Wednesday it says O which is “Low fertility” (if your not familiar with clear blue advantage) I’m just confused because she said i should be “pregnant tomorrow!” But why is my test saying low.. I’ve been havin some cramping during sex