What kind of worms was he de-wormed for? There are many types. It could be a tape worm which can be harder to get rid of. The excessive drinking is a sign of something. It could be a fever or other infection. Has he eaten some grass lately? Grass settles their stomachs. May want to take him out to eat some. Just be aware and make sure it is clean grass.
Could he have eaten something besides the food? Maybe getting into something? I almost want to say this is signs of unintientional poisoning.
It could be the dry food if you changed lately. Make sure you do throw away non-eaten food. As dry dog food can develop maggots pretty quickly. Especially if it kept wet.
Be careful of meats and bones. Meats can carry worms in it causing digestive issues. Chicken bones can cause choking.
Give the dog some Pepto bismal. Maybe a tablespoon or 2 depending on size. If he needs to vomit then I will tell you how to do that as well if need to know.
Just observe his behavior and areas he is running in. Could be licking something off his fur when cleaning. Good luck and hope he feels better!