so are you going to the vets? As water doesn't solve medical problems I'd be more interested in the cause especially as you have stated he has lost alot of weight.
I have seen members say oh the pig is better now not get medical treatment only for the pig to go back downhill because the medical issue was never addressed and sadly some of they pigs didnot make it.
A member has even went to the effort to find you a vet, I would be inclined to visit them too and get a full health check for your pig.
Of course, but it will have to be tomorrow and hence why I'm trying to get him fed up and hydrated today- I've got to try the food part next because he seems quite weak-
He'll go and hopefully get checked out tomorrow, but I just want to get some vitamins and such back in his body,