Re: I'm worried that I might have brain cancer or a brain tumor...
Hi, you don't have any symptoms at all of any type of brain tumor or problem there.
It sounds like you may be a little down from not being able to see the girl you think so much of. Stress, depression, or anxiety can wear a person down and make them tired. It can also cause dreams like the one you described, where you were hurt in the dream. Sometimes, this is your minds way of dealing with the hurt you are feeling, from not being able to see her.
Did you exchange phone numbers and emails with her?
If you have no way to contact her, the best way to get through this is to be around your close friends, and socialize like you did before. Do not sit at home alone with nobody to talk to. Go places, and do things you enjoy, and you will be surprised at how good and normal you start to feel again. It can seem impossible to do this at first, I have been there, but it works. Just don't seclude yourself from others, do the opposite, get out and have fun, and you should start feeling better.
I hope this helps a bit. I have felt this way before too, a few times, and this is what helped me.