My little guy did the same thing. I was pulling my hair out, I couldn't handle it. On a visit to the Peadiatrician for his enlarged kidney I asked the Dr about the screaming etc. and he witnessed it himself while we were there. Turns out our little guy has reflux. He said try 1mm mylanta (normal) after every feed and if that doesn't improve much then give him Zantac (he gave me a script). Well the mylanta helped a bit but not much of an improvement. We tried the Zantac and although it has made a big difference he still chokes a bit after a feed and often chucks up, but at least he is not in any pain now.
Where before if he wasn't asleep or feeding he was screaming, it was horrible. Made me think what had I got myself in for.
I would not wait, see your GP as it could be reflux and the sooner you sort that out the happier everyone will be. Good luck.