I was 10 days late for my period, always regular but got my period today. no changes in diet,sleep or exercise and no stress. what could cause this?

Some thoughts...: 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, pregnancy, etc… Sometimes a period is late for no apparent reason, but if symptoms become recurrent, one can visit her Ob-Gyn doctor for help.