I agree with all the responses you got, nothing to worry about. Our 2 year old Tiger is a full 9lb. He is just that size, and certainly not over weighted
All the tea cup toy cup nonsense is nothing else but a marketing term by all the breeders. Trust me when I tell you, you rather have a 10lb yorkie than a 3lb. You will have less health problems. When I asked our Vet if 9lb is too much, he basicaly laughed at me and said its totally normal. So no worries.
Good Luck
Thanks,