What illness do i have? serious people only please!!?

on sunday i had a headache, it went away. on Monday i woke up with a faded voice, and a small stuffy nose as the day went on my nose became more stuffy. when i blew my nose my snot was yellow. i also had some pressure in my sinuses, and i had a dry mouth. tuesday everything was the same expect the pressure in my sinuses was gone. it is now Wednesday, this morning i woke up felling just as crappy and i am coughing somewhat. i am pretty sure i know what is wrong but i just want to be sure. so what illness do i have and should i see a doctor?