Cheating parents

So I just found out that my dad is having an affair, well affairs I guess would be most accurate. I was in shocked when my mom told me and I honestly wouldn’t have believed it if it wasn’t for the evidence.

I don’t know all the details and I don’t want to know them but I don’t know how to feel. I feel sad for my mom and angry at my dad. I, myself feel betrayed because here is one of the most important people of my life doing the worst possible thing.

The worst part I guess is that everyone is pretending it isn’t happening. My mom told me to not say anything so I’m suppose to pretend I don’t know but I also feel like it’s my dad’s responsibility to apologize to me.

Or maybe I shouldn’t have been informed at all.

Should I feel like my dad needs to talk to me and explain himself ? Is it bad that I’m pretending I don’t know? What should I do? Has anyone ever been in this situation?

I’m a married 28y/o BTW. I live in my own house with my husband and my parents have been together for over 30 years.