How Do I Completely Remove Sims 3 Mods?

A while back I had the Sims 3 on my laptop and I had added a multitude of mods into the game. I got bored quickly and uninstalled the game completely. Well now I'm interested again but when I got to play the game there are no skin options, I can no longer choose male/female, and a lot of it's functionality is gone. I've tried uninstalling and reinstalling but nothing works. I've realized though that when I first install and go to play it's normal but as soon as I update it the problems occur again. Any solutions?