Help.....Penis envy.

So my boyfriend and I took a break earlier this year and he was now talking to some new girl and going on dates, which was okay because we weren't together at the time. I felt sad about it but I started talking to this guy I've always known and we ended up having sex. While we were broken up my boyfriend came to my house to pick up some things and saw a dick pic on my phone my new guy had sent me, he had asked to use my phone for some reason and I didn't mind. Fast forward to today, we got back together and cut ties with those other people and everything is fine but today we decided to watch porn together and I made a comment about how I didn't like the video coz the guys penis was rather small then he got defensive and somehow ended up linking it back to himself and how I should not say that as it makes him feel insecure because his penis is that size and he knows I've had bigger. And this is how are chats are going 🙈 I feel terrible and I don't know what to do. How do I make things better?