overreact or what?

my husband always checks out other women online, youtube, social medias... its making me feel insecure. i feel like what if he finds someone he really likes and no longer finds me attractive? what if he fell in love w them at 1st sight and fell out of love w me? i wonder all the time if he thinks theyre more attractive than me. he knows its disrespectful to me but does it behind my back. however, he checks out other women in public in front of me. how do i stop being insecure about it and just get over it? or i have a right to feel this isnt healthy in a relationship? i mean, i find other ppl attractive too, but it doesnt make me see my husband any less than them. but for him it does... because he keeps checking out women, he thinks about cheating on me. ik because when we argued, he said hes going to cheat on me.