I'm going through something somewhat similar with one of my babies right now. If you have any soft food, warm it up a little, sprinkle a touch of garlic on it and try to get baby to eat that. My girl ate that for the first time tonight and it appears to help. My vet is going to call in the morning for an update, but it seems to work. Squirt wouldn't drink anything, she was tired of milk, so we tried some soft food (which I know I shouldn't feed but we were desperate). Otherwise, if the kitten won't take that, then take a syringe and put it far in the mouth and push milk in that way. She should get about a tablespoon a feeding, but with her losing weight, you may want to push more.

Please, as soon as you know, let us know how the baby is. Our thoughts & prayers are with you.