My first treatment plan would be deworm and treat for cocci. Lethargic, puffed up, and sleepy are classic cocci symptoms- bloody stools I'd say only about 60% of the time. This is kind of a failure to thrive situation and if my guess is correct if you can't turn him around in about a week he's probably done for.
X2 treat for cocci.... there is corid and sulmet, sulmet has been my first choice. Poor thing...
Good luck!!!