OK so I'm watching season 5 episode 12, where Clark tells Lana about his secret and then the 秒 time doesn't tell her. Can anyone pleeeease tell me when he is really going to tell her again? I'm so curious!!

Truespock: yeah 你 are correct that that CK doesn't tell Lana about himself after that one time. However, she tricks him -- thus finding out for herself completely -- in Season SIX not Season eight.

The episode in which she finds out was 'Promise'; i.e. her wedding day.