YANBU @Bigjo and I am sorry for the bashing you have had on here for your use of 'they' for your husband. As has been said, can people just rein it in now. I think the OP has got the idea!
Yeah, I know/have known plenty of women who have a husband who seems to go through depression - but it's when it suits him. He is depressed and low when it comes to domestic chores and childcare, and visiting or engaging with her family (and his own sometimes!) And he always seems to be 'ill' at Christmas, and similar family events, sometimes taking himself to bed in his dressing gown of doom, and carpet slippers. Leaving all the work and the mental load, to the woman/wife/mother. But he's fine when he wants to be, when he's with his mates, and doing something HE wants to do.
One man I knew (this was a couple of decades ago,) cried out for an ambulance saying he had searing pains in his chest, and stomach, and his intestines. His wife called 999 - and an ambulance, (and the paramedics) came. He was rolling about wailing when they came. (Seemingly in pain!) He went to hospital and had multiple tests - including on his heart, and bowel, and stomach etc, and there was 100% nothing wrong with him. Not a damn thing. Normal bloods, normal blood pressure, and normal heart rate.
He managed to wangle 5 days in hospital, and it all resulted in his wife having to care for their 2 toddlers alone for 2 weeks (as when he came out, he played the 'ill' card for another 10 days,) and he didn't move out of his armchair for a moment. Only to use the loo, and go to bed. She waited on him hand and foot, and was frazzled looking after 2 toddlers too. He also managed to swerve a family wedding (her cousin) that he didn't want to go to, (but she HAD to take the kids as he was 'too ill' to look after them.) And he said when he came from hospital that it was 'ridiculous' that they found nothing, 'as clearly he was ill.'
Clearly there was fuck-all wrong with him. There are multiple stories like this from men who feign illness to avoid family commitments, looking after the children, and doing anything he doesn't want to do really. Sometimes it's physical ailments, sometimes they claim they have depression. And God help you if you are ill. Men like this don't like to be the carer!
I am NOT saying that people make up depression, and it's not real, of course it's real, but yeah, I do know some people who are depressed when it suits them, and it's usually men who have a partner/wife, and children. They act this way to detach themselves from family life and commitments.
Not much you can do though @Bigjo apart from leave him/break up with him, because he will never change. If you are separated, he will be forced to step up, and look after his own children, and actually do something for himself! I'm sorry you are going through this. 