iiKaylaOlissaii I can't tell you for sure what's causing the crash, especially with no mods to check for and report on potential problems. But what you can do from here is load the backup save. Even if you've never made a backup, the game keeps the data from the second-to-last time you saved.
Open Documents > Electronic Arts > The Sims 3 > Saves, and you'll see a folder with your save name and another folder with the same name plus a .backup extension. Rename this folder and delete the .backup, so it ends in .sims3 , and it should be available to load from the Main Menu.
If the backup crashes too, let me know whether you'd be willing to add some mods for troubleshooting purposes. They're great to use in general, but you don't absolutely have to keep them if you'd rather not.