My (21f) boyfriend (23m) is addicted to adult content. How do I deal with this?

TLDR: boyfriend can’t stop watching adult content. My boyfriend and I have been friends for 8 years. He has liked me for years but I developed feelings for him 8 months ago and we began dating. He has been amazing to me except this issue. Because we’ve been friends for so long I know my boyfriend has struggled to get women and was a big adult videos user. This made sense because he wasn’t having intimacy for a long time. When we got together this was the first time he had real intimacy in a relationship. I send him nude photos and have intimacy with him whenever he wants. He lives 40 minutes from me so usually we can only see each other on weekends. Since we have been together he watches adult videos as much as he did when he was single. He would also follow models on insta and like their pictures but since I mentioned it he has stopped.

Everyone has their opinions on adult videos but for me it’s just a boundary of mine and it makes me feel bad and I’d prefer if he did not watch it. I send him nude photos and videos and would show him anything he wants on FaceTime but he would rather watch adult videos. I don’t understand why and it hurts me so bad and makes me feel unattractive. He says he is attracted to me but he is addicted. It also affects our intimacy and he has trouble not being able to finish because of it. He’s tried to stop when I told him I couldn’t stay if he kept doing it. He did stop for 3 weeks but is back to doing it. He lied to me that he wasn’t doing it again but confessed he actually was. He told me sometimes he will do it as much as 4 times in one day. He says he’s working on it but I feel like if you loved me you would just stop. I just can’t imagine being 9 months pregnant and my husband is just watching adult videos while my body isn’t in the best shape. I already feel ugly now and I can’t imagine going through life feeling that way during times where I’m more insecure or can’t have intimacy. How can we fix this?