Questioning my fiance's sudden ual desire change?

You don't say how old he is. Has he been checked for low testosterone? That'll kill your drive faster than poop through a goose. Is he taking any medications that he started recently? Like in the past month or so? Some of them are real libido killers too. I'd get him to the Doc for a ual health checkup pronto. Low and/or no libido can be a sign of more serious stuff going on. Like heart disease,for one.