I just wrote a long reply which disappeared completely, so apologies if this appears twice!
As someone who suffered bad PND twice, I wanted to express my absolute sympathy and also to echo a pp who suggested that medication could help.
My children were born in the 80s, when PND was less well understood and accepted. My husband, who was (and still is) great was completely involved in childcare etc but had a blind spot about his hobby, which he'd been doing since childhood and which had always taken him out of the house every weekend for at least one day and often for two. He couldn't understand how anguished I felt (severely depressed and by then back at work full time) when he disappeared from dawn to dusk, living that part of his life exactly as it had been before, whereas I felt absolutely bereft. The implication was that I was being selfish, but what I actually was, was desperate. He got it eventually, but it took a loooong time and I've never forgotten how it made me feel, even though he now says he can't believe he acted as he did. I know how it is not to feel 'seen'.
I took the antidepressants available at the time, but these just made me feel like I'd been hit over the head. By the time our second child was born, Prozac had been introduced and it was a game-changer for me. Not a total 'cure' and the side effects were rotten at first, but the difference it made was profound. I took Prozac for a couple of years, I think, then gave up gradually with no prob;em. 30-odd years on, ADs are so much better than the Prozac era, with different sorts (e.g Sertraline) to try if necessary. You may decide not to go down that route, but it's something to consider.
Either way, I hope things will improve for you soon. 