Periods can vary and change due to stress, excitement and hormonal changes so there is nothing really to worry about if it was only three day earlier than usual.
Time to be concerned would be if the period was unusual in anyway such as very heavy bleeding, unusual colour or with an unpleasant odour.
If you have any further concerns see you doctor and explain your concerns and if he is dually concerned he will authorise blood tests to see if there is any problems.
