You could have a sinus infection. Your doctor can order sinus xrays to see what is going on. Sometimes you can have inflammation in there. He might even recommend a steriod nasal spray to decrease the inflammation.
Call you doctor to get some relief. In the mean time try some saline nasal spray.
You can buy it over the counter. Also try a humidifer to get things moving up in there.
The sudafed can work but it can also dry things out in there and make it even thicker.
You can also try mucinex to thin out secretions.
Best Wishes to you hope you feel better soon.