It's not unusual to have symptoms 2 years after radiation treatment. I sometimes still get symptoms, over four years out. But they become increasingly less frequent and more mild as time goes by. You can reduce the severity of your symptoms by leading as healthy of a lifestyle as you can manage. That means no alcohol, coffee, smoking, refined sugar, etc. and getting plenty of exercise and sleep.
I respectfully disagree with PaulW about tumor shrinkage being unimportant, although I suspect he was overstating to reduce your anxiety. While many tumors don't shrink after radiation treatment -- only about 25% of CK patients at Stanford University Medical Center see significant shrinkage over time -- shrinkage is a good thing because it can take pressure off cranial nerves that were formerly impinged upon before treatment. That said, tumor shrinkage is not necessary for treatment to be deemed successful. The most important goal of treatment is that the tumor's growth is halted. That appears to be true in your case, and it's a reason to celebrate and be thankful. Now, become a "health and fitness warrior" and you'll begin to feel much better over time.
Best wishes,
TW