Eating old bread as long as the old bread has no mold growth on it will not make you sick as long as it not only has any mold but also doesn't have any bad smells to it.
However if you did accidentally eat a piece of bread with a bit of mold on it and ingested that bit of mold then you'll likely be okay as long as your immune system is already healthy.
I've accidentally eaten some moldy bread before without realizing it until I noticed the rest of the bread was moldy and then realized it also by taste.
I already swallowed that moldy part of the bread and that was years ago and I'm still healthy and alive.
Expired bread is safe to eat as long as the expired bread has no mold or bacteria on the bread.
If the expired bread has just expired and it has no mold growth on the bread or has no bad smells to the expired bread then it's okay to eat.
If the bread has some mold on it then you can remove the moldy parts of the bread and eat the good parts which is what I've done before.
It's best to store bread in a cool dark place to prevent mold growth and eat the bread before expiration date because stale bread is not as good to eat.
Store bought bread usually lasts around 7 days after you buy it but some bread may last a bit longer.
But if the bread is really moldy or has a really bad smell to it or doesn't smell normal at all then throw it out.