So sorry that you are in so much hurt. Hang in there! A few thoughts…
Don’t keep your feelings to yourself! You are suffering about it, and you should not feel bad about it because you are feeling the things a person does in these situations. You are so normal, there is nothing wrong with you, it is not your “fault”. Oh boy is it okay to feel these things!
One thing my wife and I did when we had to have some very difficult conversations is to just take a night after the kids were asleep, and we would just let ONE of us talk at a time. The other’s job was to just listen, never having to think about what they were going to say in response to this or that, it really diffused the moments and allowed for better communication of hard things. Then there is always plenty of time to come back to it. We wrote a lot to each other too. But what ever you do you can’t keep your feelings to yourself.
And you are allowed to say “slow down” if you need to. Take a break… It has to work for both of you.
So be honest with your husband. And he, being a good man, will be there after all the ugly feelings are expressed. I know my wife was so scared to say so many things to me, but it was eating her up from the inside! We are doing much better for it, and I can honestly say that it was in fact some of the worst things I have ever heard her say! You have a solid relationship, you will be fine.
Just be real honest and communicative with each other, say what you need. Those are a good couple of poly rules.
Best wishes to you.