Sick snake

Your snake is cold blooded.  It may need to be warmed.  Perhaps a heat lamp might help but, be careful you don't overheat it.  Perhaps putting it in an aquarium (terranium) with items natural to its habitat. (sticks, rocks, straw).  The snake will need to be warm & not hot.  Go to the library & get a few books on reptiles & read up on your friend.  Perhaps putting the heat lamp on top of the terranium but make sure the heat can get through the lid on top.  You'll need a lid so it doesn't get out.  And he will get out.  Try putting a thermometer inside so you know what temperatures exist so you don't harm the snake.

take him to an Exotic pet hospital. Make an apointment or they will charge you more. Hope he makes it. Also by a book on how to care for your snake. heating pad is a bad idea because they can not feel pain and can burn very easy. Please keep me in touch. I will pray for him.

If the snake was active when you purchased it, you need to find out what is different about the enclosure you have it kept in.  I've owned 3 snakes in the past.  A ball python, a boa constrictor, and an albino burmese python.  The only snake I ever had an issue with was the ball.  Sounds to me like you are not providing the correct environment for the snake.  What type is it?

Aside from the comments already made; which are right - He could be molting. They get very slow, and sluggish. Are there rocks, or sticks in his cage? They use these, for stripping their old skin off. They will get a dull, dry appearance. But the comment on having a vet, with experience in reptiles see him; is the best idea.