38 weeks and nauseous!

I just hit 38 weeks this morning and I have been feeling so sick to my stomach all morning! I've been bouncing on a yoga ball and walking regularly, but I've been doing that for a while now, so I don't think it's because I'm overdoing it or anything! Anyone else run into this at this point in pregnancy? I don't want to be too lazy so this baby comes out on time, but I just feel awful!