Hello Jess! I had gone through your query and understand your concerns. I have to tell that there is no reason for a healthy child to vomit once a week or more. The fact that he vomits every week , he isn t looking well , has weight loss indicates that something is going wrong with him. I suggest to consult his pediatrician and get him examined. He need a complete evaluation:detailed physical examination , complete blood work-up, urinalysis. According to the findings further investigations may be necessary for diagnosis and treatment. Hope my answer has helped. Wish a good health to your nephew. Take care Dr.Rovena