Hope you can work it out, trying to confirm if it's lactose or the protein can be tricky. With dd1 it was 8 months of her throwing up, very little weight gains while bfing and only once she started formula top ups with lactose free milk that she refused to bfeed anymore. Dd could have a minimal amount of yoghurt or cheese but not regular milk or formula if she did she would be throwing up with thick sticky vomit. These days she has almost outgrown the problem but we still have lactose free milk. Dd2 was fine, no issues until last year she got a tummy bug and was getting sick after eating at kinder where she had been having full cream milk. She still can't have milk, cream or ice cream. Ds had issues from the beginning, reflux very low weight gains and at four months he started to loose weight rapidly the pead put him on formula top ups, and he was watched closely or ge woukd have gone to hospital, this time we tried soy, goat and then went back to the lactose free as he was in pain and vomiting. I also went on an elimination diet to see if that helped. Again like dd once he was settled on the formula he refused to bfeed anymore. So long story short two of mine are genuinely lactose intolerant, I am too but didnt realise until i was in my 20's and used to have headaches, stomach aches and bad sinuses all which stopped when I cut out milk which I love.