What Causes Left Abdominal Pain While On Medication For Breast Cancer?

I am stage IV breast cancer which is in my liver. Lately, My abdomen is taut on the left side and I am wondering if the cancer moved to another organ or if it could me caused by nerves. I take 20mg of Prilosec 2 x a day and that has helped but I still feel like there is something more going on. Scheduled for ct scan on Tuesday but not getting results until Friday. Do you have ideas?