Thick uterus lining after menopause

I am 59 years old, and I had a period after 12 years into menopuase. My doctor could not get a biosy of my uterus. She ordered a pelvic ultrasound. A couple of days ago, my doctor called me to her office to tell me about the results. I was so nervous that I  remember only half of our conversation. She told me that the lining in my uterus is thick, 7 mm, and that is the reason why I had a period in December 08. She said I need to have a D&C as soon as posible because I may have cancer. She also told me she will insert a IUD while I am in the hospital. I also need to take Provera for 14 days, so I can have periods until I go through with the procedure. If I am in such risk for cancer, I do not understand why she is giving more hormones? I do not remember why I need an IUD either? Has anyone gone through something like this? Please help me understand what is happening to me. I feel I can't breathe anymore, and I have to keep telling myself to stay calm, so I can concentrate on my daily routine and my work. Please help me!