Okay thank you. It wouldn't hurt his stomach if I switch back to his formula
They care not suppose to drink milk until they are a year old. They depend on formula for nutrients and their digestive system isnt strong enough yet. Go back to formula.
I would go back to formula, when he's a year try the whole milk again in small quantities. If his stomach doesn't handle it well you may need to try something like soy milk or another non dairy milk. Definitely talk to his doctor and see what they recommend, you can also ask to see an allergy specialist to see if he is allergic to it.
They shouldn't be drink whole milk until a year old