Hi, I had gone through your question and understand your concerns.
It is quiet normal in most of the children when you switch to whole milk from formula feed.
Body takes time to accommodate the nutritional forms.
Compared to whole milk and lactose free milk, by adding lactase enzyme to the whole milk.Lactose present in the whole milk will get digested before we drink and becomes lactose free.It makes milk sweeter.
lactose free milk is only recommended for
lactose intolerance children, all are same except this.
Mix plenty of water when you give whole milk.
Give frequent and small volume.
Give high fiber fruits,and yogurt will act like
probiotic.
If symptoms persists
consult a pediatrician and check for any surgical conditions .
Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions.