Every line here pairs a harmful act with the same two words: "i'm fine." The speaker skips meals, cuts deeper, drinks, smokes, takes drugs, and falls into meaningless one night stands. Each habit is a way of numbing pain or punishing themselves, and each is waved away with the same reassurance. The poem never says what is wrong. The list of behaviors tells us instead.
The mood is bleak and numb, with a growing sense of panic underneath. The acts get heavier as the poem goes on, and "another one and another one" suggests a loop the speaker can't leave. The repeated "i'm fine" begins to sound less like an answer to other people and more like something the speaker is trying to believe. By the end the phrase falls apart: the punctuation changes, the dots multiply, and the last "i'm fi-" breaks off. That cut-off ending suggests the mask finally slipping, or the speaker running out of strength to keep up the lie.