Oh this is such a tough time for relationships. Many do break down in the early baby years. It’s just incredibly demanding.
If he’s refusing counselling it’s going to be quite hard to both step back and take stock as you’ve got no impartial party to mediate. Doing it yourself you cannot step away from your own perspective and bias - it’s almost impossible.
The one thing that really saved our relationship after kids was improving our communication and saying what we mean. There is no passive aggressive snarking, there are no undertones or subtext.
We set down the foundations that we love each other, we respect each other and if we have issues then we talk them through honestly and without defensiveness. It’s very hard but it does get easier with practice.
You have to agree it though, that you’re on the same side.
after kids everything becomes an argument of who is more tired, who has done more, who is right, who is wrong etc. but really none of that matters (assuming one really isn’t taking on 99% of the work).
What matters is that you work on honest, open respectful communication and you stop thinking the other person is trying to score points.
Also like PPs said, you’ll be absolutely bloody shattered too. If you can then allow each other to have time off. Even if it’s just a bath or going out for a coffee.
If you want to keep your relationship you have to look after each other because that is what stops the resentment building up.
it can be done! I’ve been where you are, as have many of us. It’s brutal but we got through it and now in such an amazing place. Better than ever!
good luck!