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Take a pregnancy test and see since the periods you had were much lighter. If this is negative, then go for a blood pregnancy test as this is more reliable.
If this is negative then other causes of delayed or missed periods will have to be looked at such as stress whether emotional or physical, hypothyroidism, polycystic disease of the ovary, pituitary tumors secreting prolactin, anemia and poor diet, hormonal imbalance, unexplained or sudden weight gain or weight loss.
Please consult your gynecologist regarding this as a confirmed diagnosis is not possible on net. Hope this helps. Take care!