Hi Michelle, I'm new here too, only my 3rd post. First of all, don't be nervous the see the doc because you tend to be a bit of a hypochondriac. He has a responsibility as your PCP to check into why this is happening.
Other than the antibiotics for the sinus infection, has any other medication changed? When you were on the antibiotics did you finish the whole prescription? That is very important because antibiotics will start to clear up the infection and make you start feeling better, even a lot better, but the bacteria is not yet dead in your system. If you don't finish the whole script, they don't die, and to make it even worse, it will come back even stronger than the first go-round, and you'll really feel sick.
Another thought is you might have an inner ear problem that is throwing off you equilibrium. What about your blood pressure? Do you know what it is? Ideal for an adult is 120/80 (systolic/diastolic). If you can get to a Wal-Mart in their pharmacy section you'll find a neat do-it-yourself B.P machine where you sit in front of it and there is a BP cuff off to one side. Relax a minute, hit the red clear button, then the green button. The cuff will start to fill, 20 seconds or so later you'll have your numbers.
Those are all I can think of right now, but if I think of something else, I'll post again. Hope you feel better soon. oops. just thought of one more; you're not a smoker are you? That does all kind of bad things to a human body, because the tar and nicotine gets everywhere.