Every time I exit the game, my sim gets deleted from the world.

@zymjrb1es1nz  Just to double-check, what game version do you see in the lower-left corner of the launcher?  If it's NOT 1.67, which it should be for a Steam install, please list the full version number.

Please also try playing in a clean user folder.  Move the entire Sims 3 folder out of Documents > Electronic Arts and onto your desktop, open the launcher to spawn a clean folder, and copy over your NRaas mods, but nothing else.  Start a new save in Sunset Valley, play for a while (or just let the game run in the background while you do something else), save your progress, quit, and see whether the same thing happens.

For good measure, please also run a dxdiag and attach it to a post.

https://help.ea.com/en/help/pc/how-to-gather-dxdiag-information/