Every other line of this poem says the same thing: "I am fine." Everything in between says the opposite. The speaker cries for no reason, sleeps for weeks because of some ache, and doesn't want to talk to anyone. Each admission is followed straight away by the reassurance, as if the speaker is correcting herself before anyone can notice.
The repetition is what makes it hurt. "I am fine" starts to sound less like an answer and more like a script, something she has learned to say. She even admits she knows how to "make the talk and fake it with smile." The question "Isn't that what I am suppose to be" suggests she feels pressure to seem okay, whether or not she is.
The last line lands hardest: "I know you never asked." The mood is lonely and quietly bitter. Nobody is checking in, so the mask goes unchallenged, and the speaker is left holding her pain alone.