Lots of babies do 3 hour stretches until they're older. Every baby is different, and don't compare yours to everyone elses.
My LO has a pretty solid eating schedule and eats at 8:00 a.m., 12:00 p.m., 4:00 p.m. and 8:00-9:00 p.m. Then he gets up at 4:00 a.m. to eat again. He sleeps about 6-7 hours every night. Also, he is 7 wks old and eats 6 oz. per feeding.