<human>: Provide a brief overview of the text.

There is another post that's similar to this, I know, but our situation is a little different and I didn't want k hijack that woman's post with my own issue!

Anyways, I have a wonderful 5 year old son who means the WORLD to me, he's my pride and joy, and I hate to think about hurting him or causing him pain in the future.

My husband is Not his biological father. His biological "father" was a sperm donor who was a really crummy dude and I haven't spoken to since I was 5 weeks pregnant and never will. 

Husband and I have been together since our son was 6 months. He's always been daddy, and always will be. I just saw another poster in this sub about telling her daughter her bf is not "daddy" and realized that was something we had never even thought about! He's been around so long it never crossed my mind. 

So now I'm filled with worry that: my son will be upset, he'll be confused or sad, he won't understand, he'll say something hurtful to his dad, etc. my husband is also nervous too. Neither of us obviously want to have this conversation. Would we be horrible parents if we just ignored it, because he is for all intents and purposes his father? He's even on the birth certificate. Please don't jump down my throat if that's wrong. Like I said, this is new territory for both of us and we're just scared and confused and trying to do as little damage as possible. 

My husband is more worried about this than I am. If we have to tell him, would it be something I could talk to him about and leave his dad out of it? Or would we both need to tackle it?

Again, please be nice. This is a really confusing and stressful issue for me.
<bot>: how do we tell our 5 year old his "daddy" isn't his biological dad? Do we have to?