Will you gain a lot of weight from drinking whole milk?

Whole milk is a good source of calcium and 1 glass a day is sufficient.
But what makes you fat is not milk it is everything else you are eating plus milk.
I think it is more important to eat lots of fruit including greens, vegetables and nuts.
Because these foods are have in calcium protein and minerals.

If you look at the nutritional facts of whole milk you will see that it contains both fat and sugar.  I wouldn't recommend anyone to drink it.  It's the dairy lobbyists who try to push milk onto us to drink.

Yes you will as it will contain a lot more calories than semi-skimmed milk for example.