I HIGHLY HIGHLY HIGHLY HIGHLY HIGHLY HIGHLY doubt it is a brain tumor. Seems like a bad cold. but I agree with mele.. what is going to help your anxiety is going to the doctor and having them rule out anything scary. Colds suck!!! and can last for weeks.. sorry you're sick and I hope you get better soon!
I'm sorry you're so afraid, that is hard to go through!
I'm not a medical professional, but the symptoms you describe sound like a cold, allergies, or other sinus/upper-respiratory related issues. Are you taking anything for it? You need to be aware that a common ingredient in decongestants is ephedrine, a stimulant that can amp you up. There are decongestants out there withOUT that ingredient, though.
This is the time of year where colds and allergies are more common. I know you don't want to, but I'd encourage you to consider going to the doctor for 2 reasons. 1) they can evaluate and diagnose you, and perhaps prescribe/recommend medicines to help you feel better. 2) they can rule out any scary things that may contribute to your anxiety - such as the brain tumor you're worried about.
Anxiety stinks - but hang in there! Let us know how you're doing.