Dh & I had a very similar situation ion 2001, only I wasn't pregnant. I have no issues with porn & I knew he liked to (to use your phrase) offload now & then, fine...all part of life.
Basically, it started with him withholding affection. We have both initiated sex in the past & for some reason, he just stopped. My advances were knocked back. It started out of the blue, no problems in our marriage etc, thought sex was fine.
One day I got home before he did & opened the post. One was the Sky bill (before everywhere went paperless) and on there was several porn movies. It all made sense, why he wasn't initiating, why he was knocking me back, why we hadn't had sex for months (In that year it was 3 times).
He was getting his, at the expense of me! This was happening sometimes when I was out (understandable) & also sometimes when I had an early night.
I felt just as you did. I spent the evening crying. I didn't say anything, just left the bill out. Nothing was said.
A couple of nights later I had an early night, got up for a drink & there he was....watching porn. It was easy to confront him, having 'caught' him.
What your dh does next is what matters the most, imo. He needs to redeem himself now he knows how his actions have affected you. As with my dh, he has been insensitive & stupid. He has let porn take over & has been neglecting you.
Do what I did...tell him, in no uncertain terms how you feel. If like me, you don't mind porn, then say that, but make sure he knows that it is the fact that he was using it and not being attentive to your needs. That you feel it was a replacement for what you should be having together.
We now have a healthy view of porn here, I am not the kind of wife who tells dh what he should/shouldn't be doing BUT it shouldn't be happening at the expense of me & us.