J.K.
I have a 6 week old (my 5th) and he does the same things. I can't eat any dairy with him or he'll cry and cry and be in pain. I couldn't eat dairy with any of my children but with him, I can't even eat hidden dairy or even a tiny bit or he'll be in pain. He also gets the baby acne on his face and head and sometimes it's bright R.. All of my kids turned R. easily so I assumed this was the same thing. it'll look normal one minute, bright R. the next, then normal again. With one of my daughters, I couldn't eat corn, gluten or chocolate along with the dairy. Thankfully, she was the only one. You can kind of figure out what she is reacting to by paying attention to what you are eating and then trying to eliminate things to see if it helps her. Dairy seems to be a common thing for babies to react to. Congratulations!