<human>: I'm in a LDR with my long term boyfriend of a few years. I know he watches porn and had let me know he does. I'm a very sexual person but I really don't watching porn because I think it's fake and dirty. At first it didn't bother me because I thought he would stop once we started having sex normally. But I've found porn on his devices more than once, and everytime it makes me nauseous and feels like there is a pit in my stomach. I feel like the girls in the videos are he opposite of what I look like, and that makes me feel even worse. It feels like he's interested in other women. I've told him how I felt to and extent before and it caused an argument. He says that it doesn't mean that he has feelings for them, but it helps him relax. And I make him feel guilty because he doesn't want me to be upset. 

I think my feeling partially come from my other boyfriends lying to me in the past and claim they didn't watch porn after I caught it on their phones. 

I know if I bring it up to my boyfriend again it will cause a major argument and he will get very upset and it could damage our relationship. I don't know what to do.

Could you distill the essence of the text into 1-3 sentences?
<bot>: I'm in a LDR with my boyfriend and the thought of him watching me porn makes me sick and feels like he's cheating on me and I don't know how to deal with it.