If baby is gaining, and not fussy, doesn't seem to be in pain, and is having plenty of wet/dirty diapers, then excessive spit up is a laundry problem, not a medical problem. Babies have very tiny tummies, and immature digestive systems, and sometimes they just work in reverse. DD is way more of a spitter than my boys were. And at about 2-4 weeks of age she was having a huge spitup (or vomit, what ever you want to call it) about once every 24 hrs, with smaller spitups frequently. Also, it always looks like more than it is. I would burp her 4-5 times per feeding and that seemed to help. Even if you can't get a burp out of him, just interupting the feeding and holding him upright can help him slow down. So when he has those huge spitups wipe him off, change his clothes, change yours if you need to, and go on about life. I would only worry if he was acting in pain, stopped gaining well, or stopped having enough wet/dirty diapers.
Amanda, mama to Owen (11/05) and Connor (10/07) and Aria (12/09) Recycled Wool Longies and Reusable Baggies