What Causes Abnormal Vaginal Bleeding?

I recently had an ultrasound done for abnormal vaginal bleeding(15 days) and the ultrasound report states my luminal area of my uterus is 3mm in thickness. At the time of the ultrasound I was on my period. My GYN is really hard to get into because there are only 2 here and he has yet to receive this report because medical records are backed up too. Should I be concern and just go in there and physically hand them this report or can it wait? FYI I have HX of PCOS, insulin resistance and currently anemic. Also report showed small cyst on my left ovary. Also the ultrasound was not done transvaginal.