My Sims 4 Game is Extremely Laggy from Using Windowed Fullscreen

This happened two days ago. I was just checking out the game options, and I decided to change the viewing option. I changed the viewing from Fullscreen to Windowed Fullscreen. Then there's a pop-up on the screen saying something like, "In thirty-seconds chose it or it'll go back to the one you were using before." (it said something very similar to his I'm not sure what the exact words were)

I clicked to go back to the option I was using and now it looked like windowed fullscreen. Fullscreen now looks like windowed fullscreen.

I just ignored it because I thought it was nothing big. Then when I entered my game it was extremely laggy. Now I tried to reverse it somehow. I tried switching the options. I went into origin and repaired the game, and etc.

I do use Custom Content, I would say I have about 500 items in the mods folder. I know for a fact it's not the cc. Before I was using Fullscreen and all the mods were running perfectly fine, there was no sign of lag. Now when I changed to Windowed Fullscreen it was making everything lag.

Here's my dxdiag info.