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It is difficult to comment on the cause without examining you. Possibility of hormonal derangements, ovarian problems etc cannot be ruled out. Consider visiting a gynecologist at the earliest for further evaluation to look for the underlying cause for the changed bleeding and period pattern. Get started on appropriate treatment as indicated to regulate your periods. Be in regular follow-up with your treating doctor/gynecologist. Drink plenty of water. Maintain healthy diet.
Take care.