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Delayed or missed periods can be due to hormonal
imbalance;anaemia;thyroid problem;ovarian cyst
and even in case of pregnancy
.Since you are virgin pregnancy is out of question.You are anaemic that can be one cause and even hormonal imbalance can be present as it is common in females at your age.Please consult a Gynaecologist and get started with iron tablets to increase haemoglobin
and treat anaemia and along with that she may give you hormonal pills to regulate your periods.