Betta always hides behind plants in the tank and doesn't eat!?

My betta just started doing this 2 days ago--I thought he was really interested in his plant, but that has been there for ages and he didn't even look at it once before this happened. Also constantly is laying on the gravel once or twice before going back up to hide behind the plants-he lives in a tank, again. Whenever I throw food inside he ignores it and goes back into staring and hiding behind the plant. Is he stressed? Or should I just remove the plant and get him another tank? I'm leaving for vacation soon so this is urgent. He's up and fine now! Thanks for all the support.