Hi, MissPandaMonium. I feel your pain - I felt as if it was all of my cc that broke my game, but don't fear! It's usually one or two files that are outdated (or, in my case, actually meant for Sims 3. I am really clumsy.)
I trust that it is not the cc at fault here - it is your game files. This is because you explained taking out your custom content and still experiencing the same issues.
First, go to your Documents > Electronic Arts > The Sims 4 > and you will clearly see all of your files. In a safe place, save all of your mods / cc, and recent household saves if you'd like to keep them. (If you have any downloaded lots from places other than the gallery, save the files inside of your Tray as well. If you have no downloaded lots, there shouldn't be any files inside your Tray folder.)
It has come to my attention that from the most recent patch at the end of March, it has broken several game files. What I want you to do now is delete your Electronic Arts folder (make sure you have saved your households and cc!). Now, launch your game as normal, go into CAS and see if anything worked. Your game should have regenerated fresh files for itself. If it worked, it is safe to re-add your cc and household saves.
If your problem begins again after adding your cc back, please test each of your most recent and most oldest cc to see what the problem is.
Take caution that mistakenly downloaded Sims 3 and Sims 2 content can break your game and make it unlaunchable.
Good luck.