Fiancés fetish

So my man and I have been together for five years. I was on his phone one day and decided to google something. I found a page opened up that I found quite interesting. Pregnant porn on his pages in his safari. Pregnant women/young girls getting banged on camera! I don't find it very appealing at all. I got curious and checked his search history and he watches it almost daily when he's not around me. I've told him it bothers me but he's explains to me it's just a really bad habit and he can't stop. He told me he stopped the other day but I got so paranoid that I checked his phone again and he kept doing it. Looks like he's doing it more now. Am I overreacting or what? I'm not sure what to do. It really bothers me. It's just super strange and puts me in a super strange spot. Advice or opinions welcome. Hate will not be tolerated. Thanks!