Hi. My mom was also diagnosed last year with ascites (water) on her whole abdominal cause by the tumors. I think what they told you about the thickening in the stomach is what we call the OMENTUM wall which covers the intestines etc. Before my mother is diagnosed with ovarian cancer (even though she already had a full hysterectomy 9 years ago) she was having a hard time on her bowel, it was because of her intestines were sticking together because of the water pushing the Omentum.
I think you are right to go to the onco-gyne right away and the doctor will know what to do. Ask all the questions you want to ask your doc so you will have a peace of mind. My mom's 5th chemo is coming up and we are hoping for the best because her ca-125 level is going up and down, but luckily her bowel movements are okay now, she has an appetite, she is slowly gaining weight.
Don't be nervous, I know everybody who experienced this are scared, I am also scared for my mother but we should all stay strong to face this experience. Be positive,a lot of courage and always PRAY TO GOD, coz if we have faith in him, everything will be okay, just TRUST Him.
Take care. Stay Strong.