"one's belly is loose": (euphemistic) one has diarrhea

緩い: loose

have a meal, eat

meal / diet

yesterday

yesterday

last night / yesterday

stomach

御中: belly, tummy, stomach, abdomen; a meal, especially of rice; cotton batting; (historical) the title of a maid working in the inner part of a samurai family's house during the Muromachi period

Alternative spelling of お腹: belly, tummy, stomach, abdomen / cotton batting (from the way that batting was used in the 中 (naka, “inside”) of cushions and quilts)