W.H.Y???

Today,feel quite boring...Then,find my friend and chat with her through facebook.She asked me one question which i also don't know the answer.She asked me what happen to me besides than sickness.Besides,she said i looked unhappy all the time.I just know about this from her.I really don't know the reason why i feel unhappy all the time?Is it since this sem????Am i feel depressed?Many question mark appear in my mind.I think nobody can tell me why i feel unhappy all the time!!!