there could be many problems with your horse, but the most likely thing is that it is niether hungry or thirsty.
If your horse refuses food get a dentist to check its teeth. It might not be able to eat because its teeth might be overgrown. And about the water maybe have a word with your vet
Your horse is sick
This would be Colic.
it has colic
your horse has the impaction colic.
The horse is colicing
impacted
the animal has colic
this means they might have collic call the vet straight away if its not eating or drinking
Colic, which can be fatal. If you suspect colic, call the vet immediately!
I would say this is colic. By all accounts that horse is showing classic "colicky" behavior.
they probably have colic. HOWRSE ANSWER: impaction colic