Usually when DS acted like this, I'd check to see if he had a fever. If he had a lowgrade fever, usually meant he was coming down with an ear infection. Sometimes, though he wouldn't have a fever. Other times he was teething.
He's such a happy go lucky little guy that if he was tired, more clingy, there was usually something going on. Oh, and he ALWAYS eats better at daycare and terribly at home. Think it's a peer pressure thing.