After three months on Nutramigen I asked my paed last week why my DS was still spitting up all of the time - and sometimes spitting up breakfast foods in the late afternoon, even. All he said is that babies spit up. Lots. And some babies spit up more than others. If he's not in pain with the posset, and it's not green bile, then there's nothing to worry about. My DS will some days spit up a handful with every burp, as well, and fortunately he did so when we were at the paed's and he still said that it's nothing to worry about. It's just spit up - which is much different from the vomiting that he was doing before he was on Nutramigen.
But, agree with the others - keep a good log, and remember that pictures speak a thousand words. Take a picture of every mouthful of spit up - be it on the carpet, on a bib, in your hand, etc. Keep the time-stamp on the camera and take your camera in so the doc can skim through the pics and have a clear picture of how much and how often you are talking about. I found that my camera with pics and a couple of videos was worth waaaaay more than anything else for my doc in making a good diagnosis!