If these are very small fruits, about the size of a marble, then this is called 'June drop' and is the tree getting rid of unpollinated fruits. If you have no larger fruits (they should be about an inch across by now) then maybe there is no pollinator nearby. Also, it will need copious watering.

they also drop small pollinated fruit if there are too many for it to'cope' with. this is hormonally controlled. but lots of water will help.