Vaginal bleeding on the fourth day after ovulation is not necessarily pregnancy, but may be due to the following reasons: 1. irregular shedding of the endometrium due to progesterone deficiency, which may lead to bleeding, but this bleeding is often small and not accompanied by other discomfort such as lower abdominal pain. 2. irregular vaginal bleeding may occur due to submucosal fibroids growing into the uterine cavity and affecting the contraction of the uterus. The diagnosis can be confirmed by ultrasound examination.3. Vaginal bleeding may also occur at this time due to endometrial inflammation, endometrial polyps and other diseases with abnormal lesions in the endometrium.If necessary, ultrasound examination can be done and if abnormal endometrial masses are found, the clinical history can be combined to decide whether diagnostic scraping is needed. If the bleeding clears in 2 days and you have not had your period by the time it is due, an early pregnancy test can be done 35 days after menopause to find out if you are pregnant.