Welcome to the forum. I hope we can provide some help and support for you and your husband.
I'm not sure if you are saying your husband is struggling because he has depression or because of helping you. I get the impression he has become depressed so I hope you will correct me if I am mistaken.
First I suggest you look through this website and read all you can on depression and also on caring for someone with depression. I understand that you have been through the mill with your own depression and have a pretty good idea of what it's like. Understanding someone else can be different as we all have our own experiences. So click on the tabs at the top of the page and explore all the goodies. BB will send any of this to you on request.
Has your husband been to see his GP? It's always a good first step to get a diagnosis and a treatment plan. This can vary from person to person and can include any combination of medication, counselling, support groups etc. There are also support groups for carers which may interest you. I came across this one today. National Carer Counselling Program. The website to find out more is www.carersaustralia.com.au You may feel this is not necessary at the moment but keep a note of the website for possible future reference.
You may both be interested in attending a GROW group. These are peer support groups for those with mental illness. It's not just a weekly group meeting. The groups socialise regularly and provide support outside of the meetings. www.grow.net.au There are branches in all states.
Think about the sort of things you wanted when you were struggling. What support did you want from your husband, family and friends. How easy was it to ask for help? You have been where your husband is at the moment so try and put yourself in his shoes. I would say ask him what he wants but we know that he is likely to refuse help because he does not want to add to your worries.
I won't go any further at the moment. Other people will no doubt be along to add their suggestions. Keep writing in.