If your doctor is not helping with pain management, it's time to let them know about it loudly, or switch doctors. You should not have to live with that kind of pain.
Here is information from the National Cancer Institute
I would go through the cancer doctor for pain management, and ask them to make a recommendation. I'm a caregiver for my father, who is taking two medications for pain associated with pancreatic/biliary cancer that has metastasized to the liver. The first is MS Contin, or morphine extended release, twice a day on a regular schedule to manage pain. The second is oxycodone for any breakthrough pain. The morphine has been especially good.
Best wishes to you.