My Leopard Gecko is losing weight?

My leo is losing weight and almost refuses to eat. She has completely stopped eating crickets. She is Very lethargic, which is unusual for her. She shed last week so i wouldn't count on that being the problem. It seems as if shes too slow to catch the crickets, which is alarming because shes always been pretty fast. As a last ditch effort i tried too feed her a waxworm and she ate one, but now its been too days and all she has done since is lick some calcium dust of a waxworm. I'm not extremely worried because i know there has too be a solution. i ordered some phoenix worms cuz i cant just be giving her waxworms. ahhhhhhh what the hell.