The speaker lists everything that should add up to contentment: good friends, a decent life, strong grades, a spotless reputation. Then comes the turn on "Yet I / Don't feel happy here." The poem's whole weight sits in that gap between how life looks from outside and how it feels from within.
What the speaker feels is confusion more than despair. The questions are honest and a little anxious: is something wrong with me, or is there a reason I can't change? Neither answer is comforting. The speaker seems to be searching for a cause and not finding one.
The shape of the poem helps. The lines drift across the page in uneven indents, as if the speaker is hesitating or feeling out of place. Two words stand apart with capital letters at the left edge: "Don't" and "Belong." The final word sits alone, unfinished and blunt. The mood is quiet, uneasy, and lonely, the feeling of being surrounded by good things and still not at home.