She is 2 weeks late for her period, she already takes a pt but it says its negative, we are confused if its just late. please help us?

It happens sometimes: In a woman with regular periods, some causes of a late period include: excessive weight loss or weight gain, increased exercising, emotional stress, having an illness, traveling, medicines (like birth control pills), hormonal imbalances, etc… Seeing a doctor is a good idea if symptoms are persistent, recurring, or worrisome. If worried, can check another pregnancy test in one more week.