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Heavy bleeding during menses is a common problem and can be familial, or pathological i.e due to problem in uterus like fibroids or ovarian disorder
If you are passing lot of clots (dark thick mass)during menses then it's more likely pathologic and may result in blood loss anemia
making you feel weak.
So you have to consult your gynaecologist doctor who can examine you and if required do tests like ultrasound
abdomen and confirm the diagnosis.
The treatment may be taking hormonal ocpills for regularisation of periods or other methods depending on the diagnosis.