Are you deleting the five cache files in the Sims 3 folder in Documents\Electronic Arts? They should be deleted any time you add or remove content from that folder. For reference, they are:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package
If that doesn't help, try creating a new Mods setup, or downloading a new Mods Framework from Mod the Sims:
https://modthesims.info/wiki.php?title=Game_Help:Installing_Sims_3_Package_Files/Setup_and_Files
Don't add any of your existing mods back in yet. Either download a fresh copy of a mod you want to use, or try the two sample mods in the MTS Framework. Let me know whether the game crashes.
Please also let me know what patch level your install has. Among other places, you can see it in the lower left corner of the launcher. If it's not fully patched (1.67 or 1.69), many mods and possibly some custom content won't work.