OHHH man there's so much wrong.
You bought her when she was 4 weeks old? As in paid for her? A reputable breeder will not breed mixed breed dogs, nor will they let their pups go to new homes before they are at a minimum 8 weeks old, most wait till the pups are 10 to 12 weeks old. So if you ever purchase another dog please keep that in mind.
Get her to a vet and find out for sure if she's pregnant or not, while there schedule her to be spayed either a spay/abort, a spay after she has the pups, or a spay right away if she's not pregnant. She's a mixed breed and should not be bred, there are literally 1,000's of unwanted dogs that are put to sleep ever day in America, breeding mutts contributes the the problem.
She doesn't need milk, many dogs are lactose intolerant, if she stopped drinking it it may be because it upsets her tummy.
What dog food are you feeding her? Which have you tried?
I'm not sure if it's alright to feed raw to pregnant females, but I imagine it is, if you are going to try it your best bet is to contact a veterinary nutritionist so that y'all can figure out the best diet for her. If she's not pregnant the general rule of thumb is 80% 10% 10%. 80% raw meat, 10% bone, 10% organ. but again contact a veterinary nutritionist to figure out the best diet for her, to teach you what organs to use (please don't count skin as an organ in raw feeding), and which organs she should be getting the most of. Different organs contain different nutrients.