There are many causes of abnormal periods, including but not limited to hormone imbalance, polycystic ovarian syndrome, endometriosis, adenomyosis, endometrial polyps, uterine fibroids (especially submucosal or intracavitary in location), pelvic inflammatory disease, bleeding disorder, or rarely cancer. You should see your gynecologist for further workup and evaluation. You mentioned you have had prior unremarkable CT and US. Consider MRI pelvis, which is better for evaluating gynecologic structures (e.g., to rule out adenomyosis). Consider endometrial biopsy.
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Get an iron shot, or take a good supplement. Also, get yourself a better doctor, who will order you a uterine MRI. Ultrasounds won't tell what you need to know.
You probably need to get on birth control if you aren’t already. Birth control causes your periods to be lighter
While birth control may help, this is only masking/alleviating the symptoms. You still need to uncover and treat the underlying cause.