After being a cat person all my life, my son and I decided to love a dog. We wanted a shelter dog and got a two and a half weeks old puppy. Before giving us the puppy the shelter took him to the vet, he is vaccinated and we are still giving him a ten day tretament for worms. When Odisseo first got here he had diarrhea all the time and we thougth it was because of the deworming. The stools got harder as his appetite shrunk. Oddie takes one or to bites and stops esating. The same happens ith water, after a walk he just takes a little water. As I have never raised dogs I thougth maybe it was normal for a small dog to eat so little, but Ive seen him getting skinnier. To days ago I was so worried I tried to force feed him but he just puts his tonge out and throws away the food. This morning I tried cooking some rice and meat for the dog and he ate a little more that what he was eating (one cup of food), but did not eat anything else the rest of the day. I went to the place here Oddie sleeps and there was blood in the floor. I checked the dog and he is not hurt externaly. I took him an tried to find if something internal hurts but there is no pain. His behavior is very tranquile, he is not a playful dog but plays and likes to run with my son. At night I tried to feed him again and he did not eat, not even hen I gave him the treats he seemed to love so much. I am very scared for our dog. Im taking him to the vet first time in the morning but I would like to know what to do. Nothing like this ever happened with any of the cats I had before. Help me we are really scared for Oddie, we are in love with him and don't want anything bad to happen to him.

If the puppy is "two and a half weeks old" it is too young to be immunised and too young to be wormed, in fact it's eyes would only just be open.
It should still be with its mother...
If what you have written is true, then I cannot understand how it can be running with your child.
I would guess that your puppy is Very Sick and I would be taking it straight to the vet as soon as possible...

I would be taking him back to the vet.
The blood on the floor could have come from his stools, never a good sign.

While you may be right in that his loose stools and extreme appetite to begin with could have been because of worms or parasites you wouldn't know how bad the infestation was, it may have done some internal damage that needs to be looked at.

There are also other possibilites as to why he has lost his appetite as well as the blood, unfortunately none of which can be diagnosed without a check by your vet.

If you can, bring in a stool sample for them to do tests on, just get a specimen jar from your local chemist (pharmacy)

Did you mean he is 2 and a half months, or weeks old?