Long term radiotherapy effects and fear of relapse.

Hello.

IN 2018 I had been diagnosed with CUP cancer with metastasis in the neck area lymph nodes. After surgery, 3 courses of Сisplatin+Fluorouracil and finally a combined chemo radiotherapy soon it will be a 6th year post treatment.

But recently I have this painful/burning sensation in my neck, sometimes manageable, sometimes severe, feeling like I dont have enough skin and it's being stretched. It is hard to understand if it's inside my neck or on the surface of the skin since my sensitivity there is funky after radiation. SCM muscle becomes hard as rock after the smallest movement and sometimes without movement at all.
I keep falling into this circle of touching and palpating my neck which causes more pain/burn and muscle spasms, which causes me to touch it more and so on. I don't feel any new lumps or anything abnormal, I did MRI/CT scans each 6 months all this time and there were no dynamics, but voice in my head telling me it could be relapse and panic attacks follow up.

Have anyone who had radiation on the neck area experienced something similar? Could it be fibrosis, or different kind of radiation damage?