I haven't had a period in 2 months took 3 pregnancy test and they all came out negative?

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 (call first). Pregnancy tests are very accurate by 3 weeks after sex.