My rat won't eat or drink, and he's losing weight. The rat is sick. See a vet. You can also try feeding him some soy formula, from the grocery store. It's made for lactose intolerant babies, and you can sometimes get your rats to eat it out of a small baby bottle, even when they're sick.
Rats enjoy a snug place to sleep.
Empty milk cartons, shoe boxes, and Kleenex boxes are good examples. Look in the yellow pages for your area. Call different vet offices and ask them questions about rats. You are going to have to be able to determine if the vet knows enough about rats for you. It's either a abscess or a tumor.