I’m sorry you’re having a hard time with your breathing, it’s definitely very challenging to be short of breath from simply walking around. I wonder if the radiation is the cause of your breathing problem, they removed a tumour from your upper left lobe in 24/7, was it a large tumour, did you have any surgery with your treatment and are you an ex smoker? I asked these questions because it can explain some of what’s happening with your lungs. I had an upper left lobe removed for early stage lung cancer without chemo or radiation and a wedge removed two years later in my lower right lobe with no further treatment. I have poor breathing issues because I had COPD before the cancer so things gradually diminished with time. I’ve heard that there exercises that help strengthen your lungs, start stretching and walking more often and then try to slowly increase, don’t overdo it, just go slow and steady every day until you feel ready to increase it a bit more, your diet is also essential, lots of protein for building muscle strength, breathing exercises are good for strengthening your lungs, you can find information about this online. Also, I don’t always think that doctors know everything about what you’re capable of doing for yourself, I think that they don’t have all the answers, we’re all individuals and many people have gone far beyond expectations with their determination to do so, best wishes for your recovery.