It is possible to ovulate 3 days after your period, but the chances are small. A normal menstrual cycle lasts 28-30 days with periods lasting 3-7 days. Ovulation occurs about 14 days before the onset of menstruation. If the menstrual cycle is shortened and the menstrual period is prolonged, it is possible to ovulate 3 days after the period has cleared. Ovulation can also be affected by a variety of factors, such as changes in the environment, mood swings, etc. Early ovulation may also occur, so the so-called safe period birth control method is unreliable. If you do not plan to get pregnant, you must use effective contraceptive measures, such as short-acting contraceptive pills and condoms. If effective contraceptive measures are not taken within 72 hours of intercourse, emergency contraceptive pills can be taken. However, emergency contraceptive pills may have adverse effects on ovarian function, so they should not be used as a regular method of contraception and are not recommended to be taken frequently.