I'm pregnant. what common sense things can I not do?

Ja
It's not my first time being pregnant, but I'm hoping to not make this one wind up like my first pregnancy, which only lasted about 7 weeks. 
Anyways, In the areas of bending/sitting/lifting/cleaning, what can I not do, or what can I change in my usual housework regimen? I live a fairly sedentary lifestyle when I'm not at work or cleaning, as I play a lot of video games, so there isn't much there for core muscle to begin with.