Period 10 days late. neg. preggo test at 5 days late. on bc pill & sexual active. pms symptoms for 3 weeks now. on new medicine (citalopram 20 mg) ?

It happens sometimes: 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. Pregnancy is a cause of a missed period, if contraception fails.