I'm curious to hear from those whose LOs had or have a milk protein allergy....what were the first signs where you suspected something was wrong? What age did it start?

Something is making me think that DS might have one even though his stools seem normal. He is 5 weeks old and it's like he is a different baby the last few days- he is extremely gassy, and is having the hardest time with the painful gas. He grunts and strains what seems like all day long yesterday. Even after burping, gas drops, gripe water, he is still in so much pain. I have no clue if it's what I ate bc I am EPing and have a huge stash I the fridge that I circle through, so the milk is probably from 2-3 days ago.