Pain is imagined here as a baby the speaker has given birth to and must look after. The comparison runs through the whole poem. The speaker feeds it, carries it, and is worn down by its constant demands, while it clings to their shirt at school, in the shop and among friends. Reading closely, it seems to describe a struggle with deep emotional suffering, possibly self-harm, though the poem never says so directly. The "blood" and the "poison" given by others suggest this, but that is an inference from the imagery.
The speaker's feelings are tangled. They are exhausted and sometimes resentful, since the pain "takes and takes," yet they also feel responsible for it and strangely loyal. When other people step in and the pain weakens, the speaker catches it as it falls, asking "who else wants my pain?" The mood is dark, lonely and tender at once, and the ending suggests that letting go of something so familiar can feel like losing part of yourself.