My 3 week Pup is refusing to drink anything except for baby formula not puppy formula?

Please help me as i know it is not good for him and i haven't been able to go the vets but will be going in the morning as soon as it opens but i need a quick solution because i can see his stool is very squishy and mushy i just wanted to see if that is healthy but his urine is fine as it is sometimes light yellowish or sometimes clear colour he will literally drink puppy formula or by chance he does not particularly like this formula but it is expensive to just try out any one just to see if he will like it isn't there anyway i could try to add something extra for him to be fond of it and start drinking puppy formula P.s i would like to know giving baby formula will it become a serious danger if he was drinking it for about 3 days now as i just adopted him everything else is fine but has been acting strange since this morning as he stopped making sounds from then on, only will make a little grunt once in a while when before he was more energetic i don't understand I've checked if he was dehydrated which he's not, no diahrea no vomit, pinched back of skin regularly just in case so i really don't understand why he has refused the puppy formula would you think that he has become attached to the baby human formula please help.