Sims 3 keeps crashing?

I only have Sims 3 base game and just installed it today for the first time in the last few days. I keeps crashing now though it worked fine a few weeks back and now it only loads the game lets me pick my family and i can start to decorate and if it doesn't crash while i'm doing that it crashes when i switch to live mode. I don't know what to do anymore... i installed the update with that origin thing... is that what the cause is? Please if you have any advice!! I really want to play and install all the expansions but i don't want to even bother if the base game doesn't even want to work right.