What Causes Thick White Vaginal Discharge?

I had breast cancer almost seven years ago, had a mastectomy, and chemotherapy, 6 years ago I had breast reconstruction. I had uterine oblition about a year ago because of continuebleeding, a biopsy was done and it came back neg. now I am having whitish thick vaginal discharge, that is oderless, I have this once or twice a month. I can hardly see my period. I took tamoxifen for five years. So what is this discharge that I am having?