IMMEDIATELY up the temps at the substrate level where it is at to the upper 80's to low 90's at one end of the enclosure so it can start to increase it's own auto-immune metabolism to beigin fighting the infection. Then IMMEDIATELY make a reptile vet appointment. This is extremely serious, and your snake's life is dependant on you doing this ASAP!!!
All that you mentioned are classic signs of a very serious upper respiratory infection. If you ignore these posts, your snake will very likely die in shrt order. I have seen this play out hundreds of times with other people's snakes, so for your snake's sake, please do as suggested PRONTO!
hope the snake gets the attention and gets better soon.
~Doug
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"a snake in the grass is a GOOD thing" 
my website -serpentinespecialties.webs.com