"Why didn't you tell me earlier?" => 왜 진작 말 안 했어? ( colloquial - most likely in real life ) => 왜 미리 말하지 않았어 ? The sentence you listed is more likely to be spoken like this: 이럴 수가... 무슨 말이야? 이걸 이제(야) 나한테 말 해? (헐) 진짜 [XXXX]. 왜 진작 말 안 했어. The "[XXXX]" part may be: 미치겠네 / 돌겠네: drives me crazy. 기가 막히네: don't know what to say. 열통 터지네 / 열불 나네: drives me up the wall (makes me angry). 믿을 수가 없네 / 못 믿겠네: can't believe it (the weakest of these and least likely to be said)