Veronica-- I've been exactly the same and it is definitely compounded by the fact that I've been too tired to do a "proper" shop. I have found Jatz and Cruskits a lifesaver. I'm now into avocado or peanut butter on the cruskits- adventurous I know!!?? I also find if I carry fruit mentos or something similar that just that little bit of sugar can alleviate my nausea. When I was really struggling a week or so ago I would eat mashed potato for dinner-- yummy! Ginger beer is great as well because the ginger settles your tummy and the bubbles help you burp (attractive!)
Goodluck finding what works for you.