I've found it sometimes can be difficult to get help with pain that occurred from treatment such as surgery. Perhaps doctors don't want to feel they've caused harm. They often don't want to deal with it. My best experiences treating my chronic pain of 50 years was to go outside of the initial medical situation.
I went to a rehabilitation specialist (MD) who helped me immensely. She referred me to to a rolpher who has worked on me now for 20 years. The rolpher got me into different kinds of PT (my PCP was supportive with referral). I'm not suggesting these things specifically, as my pain is odd and unusual. The rehab doctor said something wonderful: I don't know exactly what is causing your pain but I think I know some things that will help.
I think in your case I'd go straight to palliative care associated with hospital/cancer center where you were treated. They should prescribe for pain management, and meet with you in an ongoing manner. Some centers offer therapy and chaplains if you feeling talking it out will give you some support. In my experience pain clinics can be a bit programatic--I'd get palliative care first and then go on from there. It was hard for me to accept that essentially I was on my own in terms of having to deal with the pain. I regret that I spent my 30s and 40s without asking for support. I know it sounds difficult to have to deal with this--so I hope you find at least one supportive practitioner who can help you make a plan.