Just on a hunch, there was another person that had this issue, and ended up being allergic to whey protein. This could be why your nutritionist mentioned milk based protein drinks- sensitivity to whey protein is actually a thing. Find some not based on whey- look at ingredients. Do small amounts at a time- most people it takes about 2 hours to drink a single 11oz. premade shake.
You also could have issues with artificial sweetners, which all of them have. Look for some with monk fruit, or stevia, or specifically try to avoid sugar alcohols.