As the others have said, once a pup has been weaned it doesn't need the milk and actually can have trouble digesting it. If you want my tuppence, i would stop giving him the milk and switch to a better quality dry food. You can always add a little warm water to the dry food if you need to make it more appetising to the little guy.

I give goas milk to very young pups and most are fine on it. Occasionally I have a pup that does not do well with it. There are so many alternatives and your pup is old enough not to need milk so I would just stop giving it and look at a better quality food.
As suggested by others.

I will see how he goes today and call the vet tomorrow if he is no better, thank you

Thank you I have just ordered some Arden grange for him

I've only used goats milk when hand feeding puppies. Once they are weaned I stop feeding the milk.

I'm sure you are aware, but if you are going to change your dog's food, you must do it very gradually over a minimum of 2 weeks. Start off by mixing a small amount of the new food with the old and gradually increase the percentage.

Good luck and I hope your little pup improves. I too would stop the milk, he doesn't need it. Arden Grange is good though.