Hello Laura, 

This could be due to a couple of things. One being brown marmorated stink bugs. If you saw them around your house this year, they could also be in your pears. Here's an article on BMSB: Pear: Brown marmorated stink bug | Hortsense | Washington State University (wsu.edu). I hope it is this, because BMSB can be treated for and controlled in the future! 

The second thing this could be is Stony Pit. This is a virus and can only be prevented with clean plant material. It cannot be cured or treated. There are variations in symptom severity year to year, so it will not likely be this severe all the time. Here's an article on that: Pear Disease - Stony Pit (psu.edu). 

In the future, buying trees from certified virus free plant nurseries is the only way to prevent Stony Pit from taking over your trees. 

 Best,