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Sex on the 12th to 14th day in a 28 day cycle can lead to pregnancy
. If you want to avoid pregnancy, there are some commercial emergency OC pills which can be taken within 72 hours and you mush take them. It is too early to say if pregnancy has actually occurred without proper investigations before at least the first day of missed period. These symptoms could be just indicative of a normal ovulation and do not warrant a diagnosis of pregnancy.