What would you do

Children are a blessing, God has a plan for you and your family. Just be open with him.

First start off talking with him, even if it's scary.

I did not want three children, for many reasons. I was the one that stayed on birth control even though my husband did. And the pill was successful... until it wasn't. Now here I am pregnant with our third and it was not an easy decision. We had an idea of how our life would start moving now that are girls are older. It took me months to accept it but for whatever reason we were meant to have this third baby. So sit with him and talk to him about it because that's all you can do at the moment

Edit: you'll get many comments about the baby being a blessing and it being God's plan, and while yes I have my faith, please don't feel guilty about not wanting the baby or seeing it as a blessing. It's a huge change in your life

I'd personally terminate the pregnancy in your situation