My sister had her periods started from 16th of January and it had ended by 22nd January . On 22nd January she had coitus without protection and then took the morning after pill within an hour of having coitus. Today i.e. 27th January , she is having bleeding which is brownish in colour , it is a lot more than spotting. Eventhough she had her periods just the last week how could she again be bleeding now , is this a sign that she is pregnant?