It is difficult not to be nervous facing surgery, especially when the diagnosis is unknown. However, it sounds like your doctor has a reasonable plan, although it is difficult sometimes to just look and know if it is cancer. The low CA 125 is reassuring.
The doctor can ask for a "frozen section" and get a preliminary diagnosis the same day which, although not final, can give you a good idea of the diagnosis and hopefully make you more reassured. I wish you the best.
Machelle M. Seibel, MD