If vaginal bleeding occurs a few days after menstruation, it is often due to the following reasons: 1. If vaginal bleeding occurs just 3 days after menstruation, it is often due to endocrine disorders or bleeding caused by endometrial inflammation, endometrial polyps, or endometrial cancer. 2. If bleeding occurs in the middle of menstruation, it is often due to ovulatory bleeding, because during ovulation estrogen and progesterone temporarily drop and endometrial withdrawal bleeding occurs. 3. If the vaginal bleeding occurs in the second half of the menstrual period, it is often caused by progesterone deficiency, mainly due to early atrophy of the corpus luteum, so the bleeding occurs.