Why might someone have lining of the uterus is thick?

What did your doc: Say? Your doc should have explained all of the possible causes to you, could be from too much estrogen building up benign tissue, could be form intrauterine polyps or fibroids, could be from pre-cancer- hyperplasia or endometrial cancer if you were my pt i would do an in office hysteroscopy and biopsy to r/o anything bad and then i can rec txmnent, hopefully your doc does this in the office.