It can be bad to drink too much milk as it may lead to an iron deficiency especially if the milk is keeping you feeling full where you don't want to eat other foods.
Drinking too much milk may make you feel too full and then you may not eat other foods that are high in iron.
You can then have an iron deficiency if you drink too much milk and not eat other foods.
Milk is good for you though in moderation and drinking a few glasses of milk everyday is healthy but I would not advise anyone to drink more than 4 to 5 glasses of milk per day.
Unless you are still eating properly.
If you do get a stomach ache or bloating after drinking milk then you could be drinking too much milk or you may also be lactose intolerant.
According to researchers and medical professionals drinking too much milk can cause more health issues such as with your digestive health, make your bones more brittle and can increase your risk of early death.
However you really would have to drink a whole lot of milk before it actually became a problem and got that severe.
Drinking a few glasses of milk per day is not gonna hurt you and will actually make you healthier and make your bones stronger.
If you do start drinking too much milk then you'll likely have a stomach ache, stomach cramps, bloating or diarrhea.
If so then you should slow down on the amount of milk you're drinking.