Your bitch is regugitating her food in an effort to wean her pups. She is not being sick. I know this may seem a little harsh but did you not think it would have been sensible to do a little research before mating your bitch and at least learn the basics. You waited until your pups were 4 weeks old before asking when they should be weaned. I know that everyone has to start somewhere but we are talking basics here. Most people in dogs are willing to share their experiences and knowledge with 'Newbies' but at least put a little effort into it before contemplating breeding.