=why does my sims 3 game keep crashing on MacBook?

@tvdfan1864  Please post the full specs of your Mac: everything under About This Mac except for the serial number.  And click the Storage tab too and let me know how much free and total storage your computer has.

Please also list the packs you currently have installed and the world(s) you're playing in.

2.3 GHz Dual-Core Intel Core i5

Intel Iris Plus Graphics 640 1536 MB

16 GB 2133 MHz LPDDR3

13.1

I also have seasons, pets, generations, the high end stuff pack, late night expansion pack. 

@tvdfan1864  What world are you playing in?  Some are more stable than others, and additionally, Bridgeport and the Pets expansion don't get along particularly well.

One thing that may help, as it has helped many players with your generation of Intel graphics chip, is turning down lighting and tree detail to the lowest settings.  Please do so at the Main Menu and then quit to desktop before loading a save.