Every action in this poem is cancelled out by the line that follows it. The speaker scratches, but nothing is scratched. They scream, but nothing is heard. They bleed, but there is no blood, and they cry without tears. Each pair sets a sign of pain beside the absence of any proof of it, as if the body is going through the motions and nothing comes out.
The closing lines, "I am alive / But dead," pull this together. The speaker seems to feel numb, cut off from the world and unable to make their suffering visible or real to anyone else. Judging by the imagery, the scratching and screaming could be attempts to feel something or to be noticed, and each one fails.
The mood is bleak, empty and quietly desperate. The short lines and plain wording add to this, leaving the reader with the same stark silence the speaker lives in. There is no comfort offered, only a flat, honest statement of what it feels like to be present but unreachable.