just two quick notes,

are you weighing this your self or did the vet give you the 100g weight. if you are not sure that the snake is really visibly loosing weight, i would suggest a small scale, just to make sure. i know that the stress of a non eater can cause the owner to "see" weight loss that really isnt happening. this would give you a true measure of how to plan your next move.
ALSO,
when was the last time this guy shed? if it was going into a shed, perhaps it doesnt want to eat till it finishes. i have a smaller male who gets somewhat darker, but really doesnt "go into blue" as noticeably as my other snakes, and wont eat for about two weeks of the whole process.
relax, dont get pissed, it will all work out
good luck