Oh yeah,,,It can be your sinus's. I had the same thing a few months back and thought I had a brain tumor! I didn't have any of the typical sinus symptoms, but after I had a CAT scan they found a sinus infection.
You had mentioned that you had couple infections last year. Are you sure they were completely cleared up? If not, they may still be there, or you may have chronic sinusistas which is what I have.
The only thing that got rid of mine was 6 weeks of antibiotics. Two weeks of Augmentin and four weeks of Bactrim. The doctor tried to put me on Avelox, but no way in hell. I took one pill and it made me sick. Some people should NOT take that family of antibiotics (quinolones) Very toxic to some.
Good luck with it - I know how awful that feeling is!