3 week old pup vomiting

Question
I have a 3 week old boxer which is being bottle fed, he has being doing good, but for the past day he has been vomiting, do you have any suggestions as to what may be causing this?

Answer
Delphie, I would take him to the Vet as soon as possible.  This pup could dehydrate very quickly.  He may be having a problem digesting the formula, or it may be something more serious.  I wish I could be of more help, but this could be one of many things.