What are the chances of brain tumor reappearance?

I am 27 years old. Eventhough young I fought a war in order to survive.I had brain tumor Gr II. I just received the answer from my Neuro. after radiation and of course the 10 hours surgery that my tumor was gone, I was tumor free, just 3 weeks ago. Well, as of 3 weeks after I am feeling very very weird,as I move my eyes it creates me feel as off I am not living in this world, it makes me loose balance and not feeling as a normal person as I was feeling all the time until now. I am wondering that it might be a response of the tumor eventhough I was free just recently. It makes no sense of the tumor to reappear in 3 weeks when it needs years to form. It wasnt any GBM or anything 100% fatal.