Strange feeling in head..?

I have this weird feeling in the lower-left part of my head. It's centered on a certain part, and it feels like a dull, burning sensation. It also feels kind of like tension. I've also been having random headaches, mostly sinus and stress-induced headaches. I'm really worried that this might be something lethal (I'm thinking it's a brain tumor), and am freaking out. Please give me a clue as to what this might be.