Can Thick Uterus Lining Cause Cancer?

I am 51 years of age. Two years ago I had RFA surgery because I started bleeding heavily for two months. I bled for six months after the RFA surgery and then the bleeding stopped and I have not had any bleeding since, except for some spotting on occassions, but nothing much, until this past September I had a lot of bleeding for two days. When I called my doc she scheduled a pelvic ultra sound and the ultra sound showed a uterus thickness of 18mm. A year ago the thickness was 9 and so it doubled in thickness. I am scheduled to have a biopsy again and a D/C. Does this mean I have cancer or is this a precursor to cancer? Could it be nothing?? My weight is 210. Thank you