What is the reason for menstruation to come back after 7 days?

Patient's question:

Detailed medical condition and consultation purpose:
Over the past six months, my menstrual cycle has been irregular (I have been drinking Yimucao Granules consistently during this time!). On September 15th, this period was relatively normal in terms of flow and color, lasting about a week. In October, it arrived on the 13th, which was about on time, but the flow was very light, requiring only sanitary pads, and the color was very dark, similar to the kind you see at the end of a period! It lasted for seven days. Later, in late October, I had another period, still very light and prolonged, not ending until early November. But not long after that, similar symptoms appeared again! On November 20th, it happened once more.

Doctor's answer:

Hello: Menstrual irregularities should be noted
1. Maintain a positive mental state and avoid mental stress and emotional fluctuations. Some individuals may experience lower abdominal bloating, back pain, breast tenderness, mild diarrhea, fatigue, drowsiness, emotional instability, irritability, or tendency to depression during menstruation, all of which are normal and should not cause excessive anxiety.
2. Pay attention to hygiene to prevent infection. Maintain cleanliness of the external genitalia. Sexual intercourse is absolutely forbidden during menstruation. Ensure warmth and avoid cold exposure. Avoid overexertion. Those with heavy menstrual flow should avoid consuming brown sugar.
3. Underwear should be soft, cotton, and have good ventilation and breathability. Wash and change underwear frequently, and dry the washed underwear in the sun.
4. Avoid cold, sour, spicy, and other stimulating foods. Drink plenty of warm water to maintain regular bowel movements. Individuals with blood heat should consume more fresh fruits and vegetables before menstruation and avoid stimulating foods like garlic, scallions, chives, and ginger. Those with qi and blood deficiency should increase their nutrition regularly, such as milk, eggs, soy milk, pork liver, spinach, pork, chicken, and lamb, while avoiding cold fruits and vegetables.