Ive had my period for about 3 years now & its been on time and regular but last month it was a week late & its late again. what could be causing this?

Common: Early in menstrual life, many things can cause a late period! Unprotected sexual activity, of course, may lead to pregnancy. Hormonal imbalances are common which disrupt the normal rise and fall of the reproductive hormones estrogen and progesterone. If you are not sexually active and do not need contraception, this may be watched. If sexually active, hormonal contraception either pill or implant.

See answer: Many factors can alter the delicate balance of hormones that control your cycle and cause abnormal cycles or unusual bleeding. Some of them are emotional or physical stress, weight loss and. significant exercise. See: > http://bit.ly/1CnkHXairre