Hi Yucker,
I'm not a fruit tree expert, nor a gardening expert of any type, but I there could be two possibilities for the fruit drop.
fruitlets will fall after insect damage so you should cut the fruit up and check for grubs inside the pears.
sometimes fruitlets fall if there are huge amounts of fruits as heavy set must be thinned out.
However, if the fruit drops when it is very tiny, it could be due to incomplete pollination due to a cold wet spring. Also, although conference is semi-self fertile, which means it will pollinate ok on it's own, but sometimes needs a pollination partner, a different variety which blossoms at the same time might improve the fruits pollination.
A heavy june drop could be due to irregular water supplies at the root, starvation, frost damage or overcrowding.
Maybe your tree could do with a pollination partner or a good feed and regular watering, esp considering the summers we have and the poor water table we have at present.
I hope you have a better crop this year, it is so dissappointing when fruit/veg doesn deliver, I always take it so personally.
hope this helps and if it doesn't, i'm sure someone will correct me and be able to help better.
good luck.