Cheater thinks he’s smart

My bf changed his phone passcode cause he’s cheating on me on social media. He doesn’t know I know. He also may have changed the passcode cause I checked his phone but I checked cause he’s cheating on me. I know two wrongs don’t make a right but he’s cheated in the past and this was his second chance and I had to check to make sure I had my facts right, which I did. If he mentions to me about knowing I went thru his phone, even tho he has no proof, what should I say? Should I tell him I know he’s cheating and I’m out?