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Abnormal irregular,painful bleeding is due to hormonal imbalance and is suggestive of any underlying disorder as Fibroids,cervicitis,Endometritis etc.Since it has been long you require a complete pelvic examination and investigations as USG scan and Hormonal Analysis to rule out the exact cause.
Consider visiting a Gynaecologist for thorough evaluation as heavy frequent periods can lead to anemia.
Take Care!