Get checked out!
This may be due to problems with your teeth, sinuses, lungs, your esophagus, as well as other causes.
It is getting no better, so the problem is not going away. It could be something very serious and you don't want it to get worse or get to the point where no treatment is possible! See a doc. Go to your health department, who can do some initial screening tests for free or no cost. Get started!