What do I do when stage 4 endometrial cancer stops responding to treatment?

I was diagnosed in January 2025 with stage 4 endometrial cancer at 53. Always healthy and exercised regularly. I knew something was wrong for years. They attributed my enlarged uterus to fibroids. Well 6 chemo treatments later, no option for surgery after multiple opinions, and now on immunotherapy. My CA125 went way down to normal levels after chemo but now they're creeping back up and I'm feeling worse and worse. I changed oncologist in September and am happy with him. I pray and have faith but I am scared. It's not even a year and I feel emotionally exhausted not to mention physically wiped out. My fear is to go to the ER and never leave. What's even scarier is that the general Healthcare in my area is terrible. I'm thankful my oncologist figured out I had a bile duct blockage and referred me to a specialist not in the area back in September. I'm now experiencing stomach distension and I'm praying another treatment option is for that will work and save my life.