Definitely trust your instincts on the cerial I think. I know that it would do that to me.... Make me miserable, crying, tortured. You'll heal from the cerial. Just go back to your safe foods until you feel better. It's great to know what your safe foods are, eh?
I think I just discovered that the eggs that I've been eating are the reason that my urethra has been burning. Not totally sure yet, but I didn't have my usual nightly eggs and I didn't have any burning last night, so we shall see. Food can powerfully help you and harm you.