if you don't like porn, and you've told him it's a dealbreaker for you, and he's gone ahead and used porn again... then no, you're not overreacting. that's all there is to it really.
the thing is, if your sexual relationship is a problem for him, he needs to find a solution for that. with your input, obviously.
so... sex psychotherapy,
individual therapy,
chats,
intimacy in other ways,
or frankly getting divorced. really. if you and him weren't having sex and there was no other solution, and that was a dealbreaker for him, then he should divorce you.
if his idea of a solution is to use porn, when you've already told him porn makes you feel shitty (for whatever reason - there are many reasons why it might do so!) and even less inclined to have sex, then he's a fuckwit really, and i don't blame you for not wanting to go near him. extreme stupidity is not a turn-on.
you need to decide whether you want to bother with a man who feels it's more important for him to use porn than it is for you to feel happy and secure. this is not about "having it out" with him OR sweeping it under the carpet... he's already shown you he doesn't give a fuck so either of those approaches will have not effect whatsoever.
he's perfectly entitled to use porn if that's what he wants, but he can't expect to avoid the consequences of his choices.