Overreacting to pictures

Latley I've been feeling really down about my body, I've gained some weight and I honestly don't feel as sexy or beautiful as when me and my so met. And he knows this because I've explained to him I'm not comfortable about my body and that's why I don't show it off to him like I used to.
Well recently he has been liking other females pictures in their bikinis or liking pictures of half naked girls on a page he likes... And I've told him "keep liking those half naked girls pictures and I'll find a bikini and become one of them" jokingly but at the same time serious. I've also told him before to stop seriously but I don't think he understands how I feel. Now I don't care if he looks at other girls half naked or in their bikinis, it's just when he likes their pages or pictures, showing everyone (including my family and friends that he is friends with on fb) that's the type of girl he likes/ wants and it makes me really self-conscious about my body... Because I'm obviously not that skinny or pretty... Am I just overreacting or should I try having another serious conversations with him about it? And if I should can I get some pointers to help me out in helping him understand how I feel