oh dear,I feel your pain because DS (6) is exactly the same. If I catch him doing/saying something he shouldn't, he immediately stops and starts repeating the word 'sorry' over and over again until 'the look' goes off my face. Once I sent him up stairs to his bedroom for some heinous crime or other. He proceeded to spend the next 15 mins throwing sorry cards down the stairs with variations of the phrase 'I'm sorry mummy' in them. In the end I gave in . So I have no answers for you but share your pain and therefore I wouldn't worry because it appears to be normal behaviour.