Four short lines, and almost all of them are questions. The speaker feels numb and distant, cut off from the people around them, and can't understand why nobody seems to notice or care. The repeated "Why?" works like someone asking the same thing over and over because no answer ever comes. It sounds tired and a little desperate.
The third line is the most painful: "Am I a burden to you all." It reads like a fear the speaker has been carrying for a while, and notably it has no question mark, as if they have half decided the answer is yes. Then the mood shifts in the last line. The hurt turns into bitterness. The speaker warns that others shouldn't come to them when they are "the only one you have to call." Judging by the wording, this is someone who feels used, valued only when they're needed. The overall mood is lonely, raw, and quietly angry.