Hello,
Causes of secondary amenorrhea include stress and anxiety, malnutrition,
depression, overexercising, sudden weight loss or gain (
obesity),thyroid disorders and hormonal imbalance due to polycystic ovarian syndrome(PCOS).Smoking is also associated with secondary amenorrhea. Sometimes tumors of the ovaries and brain may also cause absence of menstruation. Most likely this is due to hormonal imbalance in your case. However other causes need to be ruled out.