You r cat may have an intestinal upset (tummy bug). You could try (tricky I know!) to withhold food for 24 hours then reintroduce in small but regular meals of bland food - e.g. Boiled chicken with a bit of cooked rice added, to see if it makes a difference. If it doesnt, then a trip to the vets will probably be needed in case medication is required and to make sure there's nothing else going on that can't be changed just by change in food.