My periods lasts 10 days. had an ultrasound a year ago which was normal. what could cause this?

Please see a gyn: Hormones may not be regulated, you may have an endometrial abnormality that was not seen on us , u need a current ultrasound and then u may need an in office hysteroscopy and biopsy, us can miss endometrial abnormalities, and u may have adenomyosis, in that case u would need a hysterectomy, or u may be a candidate for an endometrial ablation I do those in office, please see your gyn.