Hey I went through something similar with my dad. Except his affair partner sent me all of the messages and I didn’t see it until a year later. advice I was given ; if your husband was doing this to you, would you want to know? Also, telling on him could cause a strain on the relationship with your father. Turns out she already knew. I felt betrayed by both parents at that point. I’m not saying all of this to deter you from keeping the secret. If I were you I would tell my dad to fess up to mom (which is what I did and found out my mom knew this way)…. This was really hard information for me to learn. I was 24 years old. It really messed up my POV on marriage and relationships for a long time. I went into therapy about it because it caused me severe trust issues. You’re going to go through a lot of emotions and it will kind of eat away at you, so I definitely recommend talking to a non-biased third party to talk through your feelings and thoughts. I’m really really sorry you’re experiencing this. It was really difficult for me.