You should have your pup checked by a vet... With both mine it was in the contract to have them vet checked within 3 days. Bring a stool sample to check for worms. (Worms are common in puppies)
Your puppy needs to eat OFTEN... at least every 2-3 hours when they are this young. Their blood sugar can get low otherwise and they can go into Hypoglycemic shock. You can read about it on the net. I free feed my puppy (I always have food down for her) and I give her wet food a few times a day to make sure she is getting enough.
Your 4 year old can hurt your puppy, so you will need to watch her ALWAYS with your pup. A bad fall can kill one of these little dogs. Don't allow you daughter to pick the puppy up. If it sits on her lap have her sit on the floor only so there is no way a fall can happen. I can't stess this enough, NEVER LEAVE YOUR DAUGHTER ALONE WITH THIS PUP! No matter how good she seems with the puppy she is to young to know better.... Please trust me on this. I have seen small dogs be dropped by older well meaning children.
You puppy needs rest. It can get sick if it is playing to much and not resting enough so make sure you give it time in the create or where ever you contain your pup so it can get sleep.
These little Yorkie's are a lot of work at first but very worth the effort.
Congrats on you new baby! We love to see pics so when you gets chance put some up so we can see the little darlin!
