Re: I'm worried that I might have brain cancer or a brain tumor...
i am no doctor but; as someone who has had a brain tumor (actually with reoccurances, i've had several) what you are describing is not cancer - it is being a teenager.
if you are still that worried about it you could go to a doctor, who will send you to a neurologist, who may order a scan for you. in addition to costing lots of time and money that process may actually leave you with an unnecessary scan (i.e. exposure to radiation). brain cancers almost always are accompanied by swelling of the brain (sever headaches). in my case i had lose of certain motor functions (walking, talking, vision), unexplained weight changes and headaches to the point of vomitting. like i say, i am no doctor; but that is what i would look for in a brain tumor patient.