perpetual happiness

its 2 am n i'm chattin wit a friend. i was practically fallin asleep a moment ago but somethin which he asked me right now has seriously woken me up. he asked me, 'how come ur happy all the time?' and i've never actually thought about it ever. i'm a normal teenager with normal teenage problems n i've never thought of myself as an extraordinarily cheerful person or anything. his question has given me a major jolt. i'm askin myself, do i really come across as a perpetually happy person? and since this question has come from one of my close friends, its even more.......provoking. its not some randon comment by a person who barely knows me. am i really so private that some of my closest friends actually think i hv no problems?? i seriously need some soul searching to find out wot exactly is goin on here. and whether i bottle things up way more often than necessary....