Try to drink a lot of water, nibble on crackers or whatever you can so you are getting something in your tummy..find things to relax you! I know it's hard at work to stop for a break but try to put your feet up or sit down a few minutes every couple hours.. Your body is going through a lot of changes and hormones are all over the place, so take it easy!
Maybe your work will be willing to give you a reduced work load with frequent brakes. I hope you don't feel guilty about asking your work for special circumstances. You have to listen to what your body is telling you, well it is probably screaming it right now. If they are unwilling to help I would talk to your OB about it. My work wanted me to travel by flying and driving to go to some training out if state but I didn't feel well enough to do so. I talked to my OB about it and she was more than willing to write a doctor's note advising against it, in fact it was her idea to do so. Your body can only take so much stress and pain before it shuts down. If you are worried that your work will be upset with your request, well, they can't do anything about it because discrimination of an employee based on pregnancy is against Federal law. Thanks America :-)