5 week old infant in great discomfort after nursing!?

My friend has a 5 week old baby who cries ALOT after he is fed. He will cry for 30-45 minutes after he nurses. His little stomach gets hard and it looks like he is just writhing in pain. He will finally get tuckered out and fall asleep. This happens probably 80% of the time after he eats. His pediatrician gave mom gas medicine and some probiotics for the baby. She also has tried gripe water. I have 4 kids of my own and never experienced this with any of my kids. Does the baby's discomfort fall within "normal" in your opinion? I thought mom should try cutting out dairy from her diet and see if that helps. I only thought of that because one of my babies was allergic to milk proteins when I was nursing. Anyone with experience with this?