Cereal is gunk that goes in his stomach and sits there to rot because he isn't old enough to digest it.
He's HUNGRY! Cereal has NO NUTRITION, it's goo to teach your baby how to chew and swallow solid food.
Formula and breast milk has 100% of what he needs. He need you to feed him as much as he wants. He cries when he's hungry so he uses a ton of energy so he eats more then he spits it up because his tummy got overfull.
So feed him numerous times per day smaller amounts and he'll keep it down and get enough.
http://kidshealth.org/parent/pregnancy_newborn/growth/gro...
This article says a month old infant should be feeding 8-12 times per day and eating about 5 ounces per time. According to what you're feeding your child he's only getting about half the food he needs.
Please feed your baby the formula he needs. You're not giving him enough food.
He should be at least 6 months old before you give him any cereal and please remember. Formula is 100% nutrition, cereal and baby food is flavored gunk that has NO NUTRITION in it. It's goo that has no nutrition and it sits in his tummy and he feels full but he gets no nutrition so he's hungry again in a bit. He gets fat from all the empty calories he's eating over and over and over but he's starving inside.