Welcome to bb and thank you for sharing your story. For what it's worth, I believe you have kept your promise as no one knows you or hubby on this forum. His secret is safe.
I did the same, only I used to call the bb support line to talk, when I was in your shoes. It was my thirteen year old daughter who was ill with OCD and anxiety and she was adamant her illness be kept a secret. Not even her grandma could know. It was tough.
There is a lot of stigma around mental health conditions and I can understand why your husband wants to protect his privacy. And, once you tell someone, you can't "untell" them. It's out there.
Your husband may not want to talk about it with others and once you share there will be questions. There may also be judgement. From our experience, not everyone we told about our daughter's illness reacted in a way that was helpful. He has to be ready for that. So do you.
Perhaps you could try and get his agreement for disclosure to one of your friends or family, to safeguard your mental health. This is what I did and it helped a lot. It's a few years down the track for us now and OCD is no longer a secret. It gets better.
If he won't agree, you can always call bb when you need to talk or vent. 1300 22 4636. You can also suggest he discuss this request with his doctors.
As for his reaction to your weekend away and overall behaviour, please try to remember that he is ill. He's not seeing the world the way you do anymore.
The bb website has great information on the impact of depression and I encourage you to learn as much as you can about the illness. This will help you to separate your husband from his illness and put things into a greater context.
You sound like an amazing support to him and he's lucky to have you.
Kind thoughts to you