My dad has been cheating on my mom for years

I’m 20 right now, I’ve had suspicions since I was maybe 11. He’s always been secretive around his phone, I’ve seen several messages between him and other women and when I was 12 I saw his tab open on an escort service. At around 14 I asked him about it, and he told me the women on his phone are “just friends mom shouldn’t know about”. It seemed extremely unlikely from the messages I saw, but I decided to believe him just because. Of course I’ve always stayed suspicious and kept seeing strange calls and messages.

Yesterday I saw him again on an escort service website. I’m not sure if he saw that I saw, but he hid it quickly and has been acting normal ever since. I’m trying to act normal as well but it’s getting really difficult. I have no idea what to do