XP - Throwing up after almost every bottle

I have 6 month old twin boys and for about the last 2 weeks one of them has been throwing up after almost every bottle.  It started with just the first bottle of the morning or the last bottle at night and has increased since then to almost every feeding.  I have decreased the amount and have added cereal and nothing seems to be working.  We make sure to burp often but the burp usually ends up being all of what he just ate coming back up.  They had their 6 month check up last week and the pediatrician didn't seem to concerned since he is otherwise healthy and it doesn't seem to bother him at all.  She didn't suspect reflux since he didn't have any trouble prior to this last couple of weeks.