Last month my period was two weeks late and had a negative pregnancy test. this month i have had this light pinkish brown discharge and blood when i wipe only. i have lower back pain and cramps and another negative pregnancy test. ?

Tests are accurate: 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. Home pregnancy tests are very accurate by three (3) weeks after sex.