You shouldn't eat mold on bread or from a loaf with visible spots. The mold roots can quickly spread through bread, though you can't see them. Eating moldy bread could make you sick, and inhaling spores may trigger breathing problems if you have a mold allergy.

What should I do if I ate moldy bread?

Ingesting moldy bread likely will not harm you, but that doesn't mean you should risk it. Give your bread a good lookover before consuming. If you accidentally eat a bite or two of moldy bread, don't panic. Simply throw the entire loaf away and relax.

Should I be worried if I ate moldy bread?

The short answer is no, you're probably not going to die from eating mold; you'll digest it like any other food, and as long as you've got a relatively healthy immune system, the most you'll experience is some nausea or vomiting due to the taste/idea of what you've just eaten.