I get 4-6 hours of sleep per night and spend the rest of the night online... but i'm fine?

i fall asleep between midnight and 4 and wake up 4-6 hours later, so between 6 and 10 depending on when i nodded off that night. but it does not affect my performance in my home schooling my concentration or anything. my doctor, when asked said i have no sleep deprivation symptoms. i wake up refreshed and ready for action usually. also, i admit to being an internet addict and it's no secret to my family, and i usually spend the more lonely part of the night playing runescape, chatting on facebook or just looking at cats. i do it during a lot of the day time too, and people say it's bad for you. bad for your eyes, makes you fat and can cause carpal tunnel, wrist and hand fatigue and other complications in that area. but i have perfect 20/20 vision, am average weight and could probably break a doorknob off on purpose if for whatever reason i had to. so what's up with both of those things? has my body adapted to the conditions? am i just built that way? is medical science wrong? wtf did i accidentally do to make my body so friggin cool?