 [ Symptoms ] what would cause me to have my period for three months straight [ Disease ] there are two major reasons for very prolongedheavy periods hormonal and what i call structural structural means when excessive bleeding is due to actual problems within the cavity or walls of the uterus some examples of this would include fibroids of the uterus endometriosis of the muscular wall of the uterus adenomyosis infections of the lining of the uterus e g gonorrhea or chlamydia polyps of the uterine lining or even uterine cancer much less likely in a younger woman hormonal causes are usually linked to missed or erratic ovulations as you may know in a normal cycle estrogen is produced all month estrogen is responsible for building up the lining of your uterus so you have something to shed each month in a normal cycle progesterone production increases following ovulation progesterone stabilizes the uterine lining in preparation for a possible implantation of a new pregnancy if you are not pregnant that month the levels of estrogen and progesterone fall triggering the release of the uterine lining—your period so if you do not ovulate the estrogen build up of the lining continues but without the usual ovulation associated progesterone thus the hormone levels do not decline and the lining stays up inside the uterus—your missedlate period alternatively the lining can begin to shed under its own weight producing prolonged bleeding  causes for not ovulating are multifold thyroid problems pituitary problems ovarian cysts physical stressors e g sudden increases in exercise crash dieting emotional stressors problems with partners workschool finances increased body weight anorexia rotating shifts at work etc 