I belong to an ovarian cancer support group, but I have stage 4 primary peritoneal cancer, which is very similar and treated basically the same. This cancer isn't usually diagnosed until stage 3 or 4, since there aren't always obvious warning symptoms.
The first symptom I had, and many in my support group had, was abdominal bloating. It looked like I was eight months pregnant. The nurse who heads the cancer support group told me that back in the day, with the swelling from all the fluid caused by the cancer, that many women were diagnosed with false pregnancy.