3 1/2 month old eating machine

Is anyone else's LO still eat every hour or two all day? My guy will eat a full meal (4-6 oz -- we know he's full because he's content and often times spits up a lot) and then an hour later be starving again. He's not an overweight baby and he sleeps well at night, but it's still a constant day of eating everyday. He gets both breastmilk and formula, but at his 4 month appointment we're going to ask about adding cereal just to fill him up a bit more.