Instagram insecurity

I am going through a rough patch emotionally in connection to the way I look and feel about myself. I’ve gained some weight and have zits when I usually have none. My boyfriend follows all these girls on instagram who constantly post naked pictures on their stories. I hate it and makes me upset and causes a fight everytime I see him looking at those posts because it makes me feel like he’s comparing me to them and makes me feel more insecure. I feel embarrassed. Even worse when I bring up my feelings about it, he gets mad at me because “he’s never done anything to make me feel like I’m ugly or not sexy”. He doesn’t understand how bad it effects me knowing he looks at those girls. Am I being too sensitive? (it is always PMS time when it bothers me most)