Should I carry on testing with opk? or when should I test with opk?

Michaela trying for baby number #3

Hi so the past couple months I haven't been testing with opks because I felt they never helped much. So iv decided this month im gunna start using them again and see if helps! I started my period 17th and finished yesterday/today, So I done a opk today, should I carry on testing from today? Or when should I start testing? Thanx