You should get some relief by using GENEROUS amounts of FESS nasal spray - it is saline, you might have to use it hourly for the first few hours until the junk starts to clear out.

A hot wet facewasher placed over the top half of your face should provide some comfort (get it as hot as you can stand without burning yourself).

Anything you can do steam wise (ie long hot shower, vaporiser) should help as well.

But finally if I were you, I'd go to the GP and tell them that it hasn't resolved since a month ago. An infection that lasts that long deserves ABs...if they won't give them, see another doctor. I'm worried particularly because of your description of the mucous - that sounds baaaaad.