Caught in the middle

I'm 19 years old and I live at home while going to college locally. I have two younger sisters and my parents have been married 25 years. At the beginning of July my parent's computer had a problem with it so I was allowing them to use my laptop because they have a business that requires internet use. I was away with a friend and my mom and youngest sister were away for a sports tournament while my dad and middle sister were home. My middle sister emailed me a picture she had taken of my computer screen. It was a list of ads on Craigslist for escorts in our area. My dad had been on my laptop the night before and apparently only closed it rather than exiting out of the browser (my dad isn't very tech savvy). My sister, who is only 16, didn't know what to do. I told her I'd take care of it. I had intended on asking my dad about it but always chickened out at the last second. So now, a month later, my dad is all of a sudden really protective of his phone. He even put a lock on it. I asked him about it and he said it was so he couldn't butt dial anyone. The only reason I don't believe that is because I work with him and we keep customer info on his phone and whenever I need to get the info he has to unlock the phone. If it were really to prevent butt dialing, I think he'd tell me the code so I could get into it during work. Also my dad is going through his mid life crisis he says. He all of a sudden wants to lose weight (he has always been a healthy weight), lift weights to gain muscle, get tan, and keep his back hair-free. One more thing is I found a travel sized shampoo/body wash bottle in his work vehicle. I asked him about it and he said he didn't remember why he had bought it. All these things are adding up to something I don't want to be true but I can't just ignore the signs. What do you think?

Confront your dad!!! I know easier said than done but girl, it looks super suspicious especially considering the Craigslist issue and the phone password. If you're too afraid, I would go and talk to mom about it because she's the one who's in the dark and she deserves to know :/ Youre the oldest sibling so you have to bring this issue up!