I have an allergy question?

my nose is ALWAYS stuffed up and my head feels like i'm in a fog, very heavy with a bad headache... this has been going on for a LONG time.. so i've gotten used to everything BUT the head fog.. i also always sound congested and tend to not be able to hear how loud i am speaking, even though my hearing is fine... It also DOESNT matter what i eat.. because I've eliminated every single thing from my diet to see if thats what it is.. what do you suppose this is? i've tried every allergy med out there and it doesnt do anything.