You need to take your puppy to the vet. If the mineral oil has not helped the puppy may have some obstruction from birth, or the puppy may have swallowed something. You did not say how old the puppy is which is very important. Please take the puppy to the vet.
Feed it lot's of fiber
Perhaps a little castor oil or mineral oil added to food. Mineral oil has no smell or flavour and less likely to put the dog off. As well make sure there is plenty of fresh water avaialble
It can be a lack of fiber in the diet of the dog and your dog is drinking very less water. Herbal supplement can be a good remedy of it. Pet Alive Natural Moves supplement is good as a remedy. For complete information visit the following link.