OPK -Do they really work?

Presley
Has anyone had success with OPK's? I'm really going to try this month.  I've just being going off my CM.  Do they really work? I was three days late.  AF came today.  I need to do something different.  It's unbelievable how disappointed and hurt I feel.  I'm so scared to get tested because I'm afraid of what the doctor might say.  I want to try everything before I got that route.  Please help me😢😢😢