@riahbearrr It may well be the mods. That doesn't mean you can't use them, but you may need to do some testing to figure out which ones are a problem. NRaas mods should all be fine—either neutral in terms of resource use or actually reducing it—except for StoryProgression. So feel free to add back any NRaas mods you use other than SP and test; then test SP separately, on one of the slowest settings (4 or 5) if you want to use it. After that, use the 50/50 method to test your other mods, then your custom content.
I realize this can be tedious, but it's the only reliable way to find the problem here. If you'd like to post your mods list, or a screenshot of your Packages folder, I can look it over to see whether anything stands out, but for most mods, I couldn't tell you for sure that they should be fine.
While testing, please also keep an eye on the Sims 3's memory use in the Task Manager, and let me know how high it is if you get an Error 12. I don't care so much about overall resource use, only what the game itself is using. If the amount is showing as a percentage, right-click the Memory header to change to absolute values. This doesn't change what you see in the header, only the values for the individual apps and services.