Betta hiding lately??

what would cause a male betta to become less active. Hide in his ornament, I hardly see him. When he does come out, he comes out for like two min. Or stays at the bottom corner of his tank. Then goes back in his barrel ornament, ESPECIALLY when I go up and look closely or come around? He will swim real fast and make laps around his tank, then hide when I get close to his tank....he never does this...Ive had him for 3 months, and he never freaks out when im around, or feed him. He never ever normally went into his barrel either....help?