i have what i think is post nasal drip,where i constantly feel the need to cough up some kind of mucus,i wondered if this could cause a sore throat and if enough was swallowed could it cause a build up on my chest.it feels like something sitting in my chest which is not sore just like something is lodge.could this also cause slight pressure in my head.please help.:p :p

Those are typical symptoms of a sinus infection that has moved into an upper respiratory infections... or an upper respiratory infection that has moved into a sinus infection. In my opinion you need to go see a doctor, get your lungs checked, and most likely take an extended treatment of antibiotics. Good luck and getting better.
Sincerely, MG