I feel sick to my stomach...

My boyfriend and I have been together for a little over a year and we have a 2 1/2 month old daughter. I was going through his phone (I don't care if I was invading his privacy, I have my good reasons for this) and looked his history. He looked up my 13 year old sister on pornhub. I wish I wouldn't have looked on his phone because now I can't stand to look at him. I don't know what to do. She's my little sister and she's 13 for christs sake! I need advice on what to do. Thank you in advance :,(  
EDIT: My sister isn't on pornhub obviously. He looked up her name on there, I'm not sure why he would think he'd find anything to do with her. Her name is unique so I doubt that there is a pornstar with her same first and last names. Why would I make something like this up? Lol people are ridiculous. I was looking for advice people. 
EDIT #2: we had the conversation I forgot to update here though. I've kinda had a lot going on. I called him out on it and he looked shocked. He didn't try to deny it or anything but he said he wasn't looking for my sister. I told him that doesn't make sense because there aren't any pornstars with her same first and last name. He searched it while we were talking to show me and of course there were none to match her names. He then said he just searched people's names. I know he's just making up shit. So right now we aren't talking or seeing each other and I don't know what to do. I told him that I'm concerned for the safety of my sister and my daughter and they are much more important than he is. I'm at a loss once again. 
EDIT #3: sorry if I didn't make the story clear. I looked in his search history, through google. So I just pushed the little star button and there is an option to view the history for that day, the day before, and 7 days previous. I selected the "today" history and it came up. The link was something like "pornhub search: [insert my sisters name]". It definitely said pornhub search and her name, and also had the pornhub icon next to it. He had gotten on pornhub and searched her name in the search box there.