I know you're disappointed now, but my Oscar is 8 lbs and growing--he will probably be about 10 lbs by the time he is done. Now that I have him, I realize just how robust and sturdy he is, and I'm glad he's not a tiny Yorkie. Very small ones can be so easily injured if you're not careful.
Give it some time. The disappointment will go away, and you'll will find that you can't live without him.
Just a sidenote, from what I understand, there can be quite a size difference between litter mates, and just because the parents are small doesn't always guarantee that their babies will be. Your breeder may not have been trying to deceive you. She probably honestly thought that your baby would be small.
Take care, and keep your chin up!
