What does it mean when your period is late but pregnancy test comes back negative?

About missed periods: In a woman with regular periods, some causes of a late period include: excessive weight loss or gain, increased exercising, emotional stress, having an illness, traveling, medicines (like birth control pills), hormonal imbalances, etc… Seeing a Dr. is a good idea if symptoms are persistent or recurring. Home pregnancy tests are very accurate by 3 weeks after sex or 1 week after missing a period.