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As such there can be a variety of causes of missed periods like hormonal imbalance, weight gain, weight loss, PCOD, thyroid dysfunction, pregnancy to name a few. The chances of pregnancy are less likely with negative urine pregnancy test if performed recently.
Hormone fluctuations can occur due to changes in diet, changes in sleep patterns, exercise routines, stress levels, etc. It can also be caused by any new medications even over the counter supplements or any recent illnesses
You should try vitamin C supplement, ginger tea, pineapple, parsley tea, maintain weight, do deep breathing to induce a period.
Otherwise, you should consult your gynecologist and your doctor may advise some form of progesterone to induce a period and further investigations like ultrasound, blood work like Thyroid function test, LH, FSH, etc may be advised for further diagnosis and management.