Milk sensitivity seven week old baby boy

Recently maybe about three weeks ago my sweet angle was told he has a milk sensitivity and I breastfeed. He is on nexium and has gripe water and a probiotic Incase he still uncomfortable. I have been drinking almond milk and I messed up and tried a friend of mine snack and it had butter in it. That night my son was grunting so bad and just didn’t seem himself. His dr gave me a dairy chart on Thursday the day before I had the cracker with butter so I can try to introduce milk back in my diet but since I ate a tiny bit of butter I totally feel like I definitely can’t have any milk still. We have a apt in March for a g.i dr but I wanted to know what advice you have for the grunting and if that tiny bit of butter hurt him just the way before I was told about the sensitivity? I feel just awful about the grunting. I thought it was the almond milk that upset him but now I think it’s the butter.