I think people feel ashamed if they do not toe the party line about having children, so they try not to moan. It is incredibly difficult. I did not have my first until I was in mid-30s and naively thought I would not regret the loss of my previous life, because I have had a really adventurous, lucky and happy life. So I thought i would settle in with no regrets.
I think I had pnd, but was so stressed out trying to make out it was all perfect that I was in denial. You love them, hugely, but that still does not mean you do not wish they would vanish and you could have a day of your old life back.
I recall once having coffee with a colleague who seemed to have it all- the baby, the affectionate husband who seemed to sail into fatherhood (where DH did not) who came back from mat leave TO a promotion (I stagnated) and she asked me if i would have another. In a fit of honesty i said that there was no way. If we did, we would divorce because we really barely surived DC1. Then it all came out- how hard it was, how they were having marital counselling, how sometimes she wanted to get on a train to scotland and just vanish from her life. That was when i realised that it is like this for most people, and we all are trying maintain a facade.
We have hit our stride now as parents, and have had more DCs, and i am really in a good place. But it was hard. Not hard work...I do not recall working at it, more enduring but everything seems now to have slipped into place and I am loving being a mother and a parent. I ALWAYS love them to fight to the death for them- that is what you do- but for now it is easy.