Need to be evaluated
can be due to hormonal problems or due to anatomical problems like benign growth from the muscle of the uterus
called fibroids, polyps in the lining of uterus or less likely due to adenomyosis
(this is a form of endometriosis
of the uterus).
No matter what , prolonged heavy periods can make you anemic .
You would really benefit from seeing a gyn , and getting an ultrasound.