labrador milli

Question
how much should my 17 week old puppy weigh

Answer
Nobody can say.  40 pounds might be typical, but your puppy could be quite different.  

Weight is a poor way to judge a dog's condition.  Go to http://www.puppychow.com/products/popup_body_condition.aspx  Evaluate her and adjust her food as needed to reach her ideal body condition.  I would also switch to an adult chow. It slows growth allowing more time to develop strong joints.  Along with keeping the dog lean, it is the best thing to do now to avoid joint problems.