What types of symptoms can happen from eating mouldy food like bread? What would be the worst/most serious symptoms that would require seeing a Dr?

Mold. Mold is a fungus, it estimated that about over 300,000 species exist, and bacterial contaminated rotten food should not be eaten Symptoms vary according the bacterial type and load. Range varies from dysconfort, diarrhea, dehydration, bronchospasm, sepsis. anaphylaxis, and death. Mild/moderate may be managed at home, more severe in the ER, to replace fluids, and treat schock.
Problems unlikely. The danger is small, but real, as a small number of mould species produce toxins called mycotoxins (fungal toxins). Even if present, unless conditions were just right, no toxins may have been formed. Most cases recognized have occurred by ingestion of foods made from contaminated grains. So, it is unlikely that you will have any ill effects, impossible to say when.