Three short lines, and a small scene: someone is outside in a garden, unwell, with a stomach bug. The title, "Convalescent," suggests they are on the mend, or at least resting and recovering, though the poem itself never says how far along they are.
The most interesting phrase is "I cannot help the bug / in my stomach." It works two ways. The speaker can't do anything about the illness, which is a plain, rueful shrug. But "help" could also mean they can't assist the bug, as if it were a small creature living inside them that they have no say over. That gives the line a dry, slightly comic edge.
The mood is gentle and still. The garden suggests fresh air and slow recovery, while the speaker sounds weak, patient and a little humbled. Nothing dramatic happens. The poem simply sits with a body that has stopped obeying its owner, and finds a bit of wry humor in that.