hello Sad carer, I'm terribly sorry that your post has slipped through the cracks, unfortuntely this can happen, especially if the site is very busy, because before you know it your comment has been put onto page 2 or 3 and then can be missed.
It's a long time being married and I'm sure there were many a happy a time for the two of you, however depression can and will destroy any r/ship as it did for myself.
You have always been there for him and no it's not his fault, but for whatever reason his depression will slowly begin to create problems, no matter how strong you feel as though you are, it will begin to affect you, that's how strong depression is, it's terrible, horrible and I could use more explicit words but they wouldn't be accepted on the site.
As scary as it may feel there is life for you on your own, although it's a situation you haven't been in before for such a long time, and that's exactly how I felt after my 25 year marriage ended, but I turned my life around completely, well I had too, I couldn't stay doing what I'd been doing before, simply I didn't want to, nor did I have any desire to do so, I had to find strength some other way, so here I am.
There will be memories both good and bad, but at the moment it's the latter that has all the strength, but you won't forget the times you enjoyed, and even if the marriage seemed to improve that doesn't mean that you won't be in the same situation you're in now, and don't be afraid to go your own way, trust me it does get better.
You will always love your husband as he was in the good days, but take a break if that's what you want or decide to separate it seems as though you've been through a great deal, and I hope that you go back to your doctor, just by yourself. Geoff.