I wanted to help set your mind at ease. I also had stIV O.C., surgery, and my CA125 was elevated after surgery. My surgeon said this was usual, for it to be elevated after such a procedure. I don't know if this is a rule, but it did happen in my case and was confirmed by my surgeon.
My CA was 15 at the time of my second surgery. Post surgery it was 155. This was a direct result of the surgery. It took about six weeks for it to return to single digits.