First things first, congratulations on your pregnancy
Our number 5 was a surprise, after we thought our family was complete. It threw a spanner in several plans
I remember shaking as I tried to gasp out the news to dh - I was almost hysterical! However just today i was looking at her and thinking: if it had been purely our choice, this little person, who brings us so much delight wouldn't have been here. I'm grateful the decision was taken out of our hands.
Unexpected things happen - both good and bad. All we can do is roll with the punches and make the best of it.
I'm sorry the last 18 months have been so rocky for you. Do you have a counsellor you can check in with, to work through how you're feeling at the moment?
Also I've heard others suggest that perhaps you don't tell dh face to face. That way he can react in private - just as you've been able to do - and then you can move forward together. Would that work for you? Or do the two of you work best if you can discuss face to face straight away?
You might like also to head over to the large families section. They are a very supportive bunch, and have loads of ideas of managing a larger-than-average family.
I wish you all the best!