잠이 안와.

못 자요 = I can't sleep I am sorry. I forgot the space and this shorter form should be enough to tell someone that you cannot sleep.

SISTAR's song "Alone" , 오늘도 잠 못자 = I can’t sleep again tonight

잠을 못자요

난 잠을 잘 수가 없어 or something like that.