It sounds like your doctor
(or someone else) gave you a diagnosis of paranasal sinusitis. This is just a fancy term for a sinus infection. The sinus are spaces within the skull bone that typically don't cause any problems. They normally drain a small amount of fluid down into the nose passages that we don't really notice that much. Sometimes a viral infection can cause inflammation of the nose which can cut off the sinus drainage causing the fluid to back up into the sinuses. This causes them to become infected with bacteria. The increase fluid within the sinuses causes pressure which can be quite painful. Sometimes it can feel like your head is going to explode. Most sinus infections go away on their own. Once the viral infection (such as the common cold) fades away, the sinuses can then drain effectively and the infection is washed out. Sometimes this doesn't happen very fast, and we use an antibiotic to accelerate the process. In your case, it sounds like you are miserable and should be treated.
I suggest that you schedule an appointment with your primary care physician
. He or she can take a more detailed history of your symptoms and perform a thorough physical exam. From there your doctor can prescribe a decongestant, and antibiotic, or both. I hope you feel better.