Yup, millet could definitely do it. I used to try to eat it, but suffer an attack afterwards.
We do, though, have to try new things, so kudos to you for testing the waters with millet. Maybe try quinoa. It's much more gentle! Millet gives me much worse attacks than oatmeal. Actually, brown rice is nicer to me than millet or oatmeal. But they're all mean!