Game keeps crashing...

My game keeps crashing. It will be going fine and then it starts to get really glitchy then crashes. Also - I can't complete the newest quest because every time I go to the library in Willow Creek it doesn't load. It just stays on the blue loading screen and I can hear my sim moving and talking in the background but it won't load, so I have to force quit the game and lose everything if I didn't save it. I have tried it with and without mods, and I have repaired the game but nothing helps.