Yes, a bit more info might help.
How old? Have you taken a stool sample into the Vet to be checked? If not, I would do that to rule out parasites, etc.
Yes, what food and have you switched foods?
Welcome...This could all be food related......Can you give us more information? What kind of sick do you mean? When was he last wormed? What does he eat? Any table foods? How about treats? Anything else would be helpful......Thanks, Karla