An early PET scan often shows scar tissue as cancer when it is not. Even after years that can be the case, but if they continue to compare scan to scan they can get a better idea as to what is real and what isn’t. PET scans are useful to help with diagnosis but they are not the final word nor should they be.
You sore muscles are very common after radiation. Many people including myself experienced nerve pain, twitching, and numbness for several years. The fact that you are working a physical job although difficult, is probably a good way to keep in shape and help heal, tough as it can be some days.
I traveled for work. When people I met saw my red neck and face they formed an opinion about me that led to incorrect conclusions. I let them talk stupid for a while and if it would persist, I would then tell them about radiation treatments which would shut them down in a heartbeat.
You will probably worry that every little thing not normal is a return of the cancer. Most likely it is not. It’s normal to feel that way for a long time.
It’s also ok to see life differently after your experience. How can you not? You have earned a second chance. The healing over the next two years might at times get you down but eventually you will get back to something close to where you feel great again. The healing from radiation damage takes a lot longer than a broken bone or a sunburn, a lot longer. Be patient along with the courage you have.