Any tumor is not supposed to be there. The brain is only given so much room. When something infiltrates it, SOMETHING, SOMEWHERE, generally goes pretty wonky. That's not always the case, though. There isn't really a typical "brain tumor." They don't all present the same way.
I'm willing to bet though, considering you're on a health anxiety board and post very frequently about a wide variety of things, that you do not have one despite what you might be feeling. Your health anxiety is likely the culprit. Treat it, and everything else will follow.