What would you do if your partner makes a negative comment about your body and then apologizes?

(I'm a gay man btw) My boyfriend of 4 years and I where having sex the other night, when he suddenly couldn't get it up, he told me it was because he wishes I had a bigger butt and then a minute later because he'd like me to be more masculine... I couldn't believe what I was hearing, I threatened to break up with him and we supposedly solved things after he apologized really deeply.. He claims he says alot of things without thinking clearly but I don't 100 percent buy it... I have very much cared about him and have done alot of things for him until now... I have been feeling lately (before the comments even) that our relationship isn't as fun and intriguing as it was in the first year of dating... If I don't stay with him I do want to be friends with him... He was very apologetic and I'm sure he meant it but I feel very confused and unsure if I want to stay with him. In addition to that I was planning to marry him until now, now I'm terrified of commitment.. I also feel like there must be someplace those comments came from apology or not...