Bitter Milk

There is something weird in the C***** fresh milk. It tastes extremely bitter so much so that my 2 year old has been refusing to drink it recently. I tasted it and although not spoilt, it has a very bitter taste. The taste is not evident when added to coffee or tea. But if drank as is or even to cereal this bitterness is quite evident. I have bought the fresh milk from 4 different stores and the result has been the same. Earlier today I decided to try long life milk instead which was a different brand just to see if there was a similar taste. And there wasn't. This milk was actually pleasant tasting. C*****, please have a look so as to see what may be causing this bitterness.