CA19-9 going up and back pain at night - recurrence?

I was diagnosed with pancreatic cancer in July 2022 - stage III, borderline resectable. I had 12 treatments of FOLFIRINOX and followed by a Whipple surgery at the end of January 2023. My margins were all negative, but 1 of 11 lymph nodes was positive. The pathology report after surgery suggested that my cancer is actually a cholangiocarcinoma (bile duct cancer), which is different but similar to pancreatic cancer. Since surgery, I have had CT scans and blood work (including tests for circulating tumor DNA and CA19-9 levels) done every 3 months. The CT scans have not revealed any metastasis and my ctDNA tests have detected no tumor DNA. However, my CA19-9 has gone up over the past 6 months, from 7 to 28 to 76. This has me concerned, as the number only dropped from the time of my diagnosis through surgery (see attached graph). I have also recently started experiencing back pain at night, something that I had before my diagnosis, but that went away during my treatments. This also makes we worry. My oncologists suggests to wait for the next round of tests in another 3 months. Is there anything else I should be thinking about doing? I am currently receiving no additional treatment.