Why my period last to much ?

Time to see your doc: If you see a doctor for heavy periods, they will want to make sure that you don't have any fibroids (usually benign tumors of the uterus) or polyps (growths of tissue from the uterine lining). If you have always had heavy periods, you may want to make sure you don't have a bleeding problem in general. Sometimes there is no definite cause, but knowing it isn't cancer is a must. Next, treat it.

Adenomyosis: Sometimes the lining of the uterus invades the muscle of the uterus causing pain &/or bleeding. This is usually seen in women who have had children. The only successful treatment is hysterectomy, but ...I agree that all possible causes should be looked at by biopsy &/or ultrasound.