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Emergency contraceptives work when taken within 72 hours of unprotected intercourse. Usually if it is successful in preventing pregnancy, you should get withdrawal bleeding after 5-7 days of taking the pill. Your recent symptoms of headache, breast soreness, increased tiredness, weight gain, mood swings could be suggestive of pregnancy. Visit your gynecologist/obstetrician for examination and tests (blood beta HCG levels) to confirm/rule out pregnancy.
Take care.