Coping with work

I'm in a pretty fortunate position where I can generally choose the hours I work. But I've been feeling so ill this past week and my commute is 2 hours one way so have stayed home. My boss knows I'm pregnant but I feel he'll stop being understanding if I continue to not actually be at the office. I feel like the sickness is only getting worse and don't know what to do. Those of you who work and also feel hungover every day, how do you manage?