guinea pig,

Question
my guinea pig doesn't seem to want to be in his cage, but when he is he just sits in one corner, he wont eat or drink, but he'll accept stuff like lettuce?
he doesnt seem to have alot of energy?
help.

Answer
It's difficult to say why he's behaving that way without knowing a little more. Does he have energy when he's outside his cage, or is he acting like this all the time?  

It's a good sign that he will eat lettuce, but it also raises the question about why he can't or won't eat anything else.

There are a couple of things you should look at. First of all check his teeth. Make sure he doesn't have a malocclusion that prevents him from being able to eat or chew his pellets. Sitting in a corner in the cage is always a red flag that something is not right.

The lack of energy is concerning.  I think it might be wise to have him looked at by a vet. Guinea pigs can lose weight quickly when not eating or drinking. So before these symptoms progress take him to be examined and make sure he doesn't have a physical reason (like a dental problem) that is keeping him from getting what he needs.