I had my lmp on 14th feb and i was last sexually active on that day.i tuk 2 pregnancy test on 14th march and 3rd march both negative my period is late?

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, etc… Seeing a doctor is a good idea if symptoms are persistent, recurring, or worrisome. Pregnancy is the common cause of a missed period, if sexually active.