HI I may have some insight. Im not a professional just another cancer survivor whos dealt with other chronic illness so feel free to take this with a pinch of salt but I started getting some similar symptoms to you about 5 years ago and even put a similar post on here myself at the time, now im being tested for something called POTS. It doesn't mean thats it in your case but may be worth looking it up to see if you relate, people with pots are often misdiagnosed/undiagnosed for a long time. I've also heard it can sometimes be linked to chemotherapy. Fibromalygia may be something else to look into whch is often caused by extreme stress and traumatic expereinces such as going through cancer, I've dealt with cfs which is very similar. But yeah I dont think its that uncommon to have effects so long after. I've heard quite a few people have. I hope you get some answers soon when you go to the neurologist. :) I know how frustrating it can be to not have answers!