A support group may be just what you need and I hope you find one, but if not, or if it doesn’t assist in quite the way you want, consider a one on one with a professional counsellor - one who has experience with cancer patients. I asked my senior oncology nurse about a support group when I ran into some unexpected side effects. She was pretty astute and while happy to assist also recommended an excellent counsellor. I only saw her for a few months, every three weeks, but she sussed out what I really needed pretty quickly and gave me some excellent tools that I still use over a decade (and no cancer) later.
Best wishes.