I've been careful to always get updated mods and stuff, but I got a message before I started my game saying that I had out dated modifications. I'm unsure how I can find them since I have a lot of CC. I've experienced weird glitches like not being able to save and randomly being re assigned houses. I've tried deleting my most recently downloaded but it seems they weren't the culprit. I'm on a macbook pro.

I think that this message only refers to outdated scripting mods, so you can at least exclude all custom objects, clothing etc. and can concentrate on all mods that change the game behaviour. And if you know which of your mods are only tuning or xml mods you can exclude these, too. Well, these can be outdated as well, of course, but whatever causes this message probably doesn't recognise them either.

Actually, if it's the one I'm thinking of, that message should only appear when the game detects an outdated core mod. The game can't really tell if other kinds of content are outdated, but for core mods the patch version numbers have to match exactly and sometimes there must be different versions for Steam vs. Non-Steam installs (Mac players would use non-Steam). Outdated script and tuning mods that don't crash the game tend to load without warning, just not work well.

If you happen to be an NRaas user, the only two mods in our collection that are core mods are UntranslatedKey (of interest only to developers) and ErrorTrap, the rest are script mods and tuning packages. AwesomeMod is a popular core mod. So is CmarNYC's XCAS. There are others, but not nearly as numerous as other kinds of content.

To help narrow down the culprit, you might want to remove all mods except the ones you are certain aren't core mods and see if the warning message still appears. Then add them back in batches, or by halves if you have a lot, until you can isolate what's triggering the message.

The other possibility, though a little less likely since apparently this error message didn't appear before, is that you have an incomplete patch job on your game that has until now gone undetected. If you intend to be playing on Patch 1.67, the SuperPatcher can fix that. Make sure to get the correct regional vs. Origin version for OS X if you try this and if it says you are already up to date, make it run anyway. Can't really do any harm other than waste time if it doesn't help.
http://help.ea.com/en/article/the-sims-3-super-patcher

I only have ErrorTrap, I'll try removing it and see what happens!