I need advice-

My boyfriend is out of town on a hunting trip, and I’m house/dog sitting for him. I was using the printer in his office when I noticed this drawer of childhood pictures was slightly open (he had shown me pics from this drawer before). I wanted to look at more pics so I opened the drawer. Right behind the pics were journal entries and worksheets from counseling he’d been in. He’s been a lifelong alcoholic but is now sober, but was in rehab many times. Anyway- in these journal entries I discovered he had cheated on his ex wife with two different women- one who used to work for him. He has always been ADAMANT he never cheated on her. They were married for over 20 years and according to him- she would withhold sex constantly. I would always ask him if he was sure about that since he was an alcoholic back then, and he would say over and over again who he would never cheat because he made his vows to God and blah blah. He knows I was cheated on in my previous marriage and it hurt me deeply. Well what is bothering me the most is the fact that he is EXTREMELY insecure, controlling and jealous! He is always accusing me of being with someone else, wanting to be with someone else, worried about men who comment on my social media etc etc. it’s so annoying but I just chalked it up to our 17 year age difference (he’s 52 and I’m 35). But now I just can’t look at him the same. I get him from the airport at 5 tomorrow and I’m not sure how to react to this news. He’s a prominent dentist in town and is always saying he would never mess with any of his girls that work for him, but according to his journal entries, he did in the past! My dilemma is- should I confront him about this? Then I would have to admit I read his private notes, even though they were not hidden well at all. I know I need to decide if I want to move forward with someone who is clearly a liar, but if I just up and break up with him with no explanation, he’s gonna wonder why… but if I tell him how I know, he’s gonna be pissed. Please help me decide if I should tell him I found out from reading his notes or leave it alone and try to move on? This is my first post like this.