Period 4 days late, pregnancy test negative. should i be worried?

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 (such as hormone pills), hormonal imbalances, being near menopause, etc… Seeing a doctor is a good idea if symptoms are persistent, recurrent, or worsening. No worries yet.