Is this mainly at the back of the fridge? If so it sounds like the door isn't shuting/sealing properly so the fridge keeps trying to get colder and colder to bring the whole temperature down to what it thinks is correct. The other possibility is that the thermostat has broken and it doesn't know what the temperature is.
If I put things on the bottom shelf / in the salad boxes then they tend to freeze. Try putting your milk in the shelfes ont he door or on higher shelves?