Feeling extra insecure

My boyfriend of 4 years started liking all these pictures of girls on fb. I know I know 'it's just fb', 'get over it', 'grow up', ect. I've never had a problem with Facebook or being jealous but for some odd reason I've been feeling really insecure about myself. I just feel like he likes pictures of girls with pretty smiles, I don't ever smile showing my teeth. Or nice bodies, I've been feeling like I'm gaining alot of weight lately, I haven't worked out so my legs and butt are getting jelloish. Nice natural hair, my hair has highlights all over and has been getting really burnt and ugly. I'm just sad, I don't want to bring it up to him because I know it's no big deal that he likes pictures but I don't know, I'm just not happy with myself right now and I'm not sure if it's because of the pictures he likes or because I'm just getting ugly lol. But in all seriousness I need advice :(