Third trimester stomach issues

I am currently 28 weeks and in the last week and a half no matter what I eat or how much I feel like I am going to be sick.  This can last for hours.  Even when I drink water.  This is my second child and I did not get like this with my first.  I am smaller this time around too.  Any suggestions on how to keep food down or could it be caused from something other than baby?