Oh that hurts!

My baby keeps biting me when I nurse. I can't take much more of it, I had stopped him nicely, and have told him that hurts, I have even yelped, because dang that hurts. He cried once, every other time he laughed.  The last time this happened,  it was just as the mail was being delivered outside of an opened window. I wanted to cry, and the person outside must have heard me saying "No, No, No" because they stopped and listened.  I am sure they now think I hate having the mail delivered, if only it was that easy.  That I could fix, but this biting thing, is a whole other issue.  Babies shouldn't leave bite marks.