Hi KSQ, welcome to MB. How much of Harley's site have you read? A great place to start when trying to improve your marriage is sitting down and just putting in the time to read and understand what Harley says about what makes marriage work. Reading his stuff can really help demystify the illness in your marriage and help you understand what makes you and your husband tick. Instead of this seemingly unsolvable problem you'll find that there are lots of things you can do to get your marriage back on track.
Basic Concepts First off, if your husband is depressed he really does need to see a doctor. Depression often requires medical treatment along with counseling. It is not a problem people can or should just try to manage on their own. But remember, this is your husband's choice. You cannot control him and should not try. All you can do is express your opinion and respectfully request he see a doctor about his situation. Once you have expressed this desire and he has responded to you - you need to drop it. Don't keep bringing it up. He knows how you feel. Saying it again doesn't do anything positive. He probably doesn't want or need someone to parent him.
Next I would really get in to understanding your and your husband's emotional needs. If your husband isn't interested in talking about his needs now, do your best to figure them out and become an expert at meeting them. You need to learn to put much more in to your husband's lovebank than you take out.
Emotional Needs EN Questionnaire Also take time to figure out your lovebusters and completely eliminate them. Only you and he can figure out what those are but he has already given you a hint - he doesn't like talking about the situation and he feels like he is being nagged. You have to stop doing things that are irritating or otherwise produce a negative reaction for him. Everytime you do something that produces a negative response in him you are punching a hole in his lovebank. When being around you is unpleasant, he will desire to be somewhere else.
Love Busters LB Questionnaire Depression is a challenging situation and it certainly can put a strain on a marriage. But I get the impression there are things you can do, adjustments you can make to the way you respond to him and this situation that could take the negative focus off your marriage. Sounds like stopping the lovebusters is the first thing you need to do.
Finally, no good member of this forum would fail to at least ask - any chance he is having an affair? Spending time at someone else's house seems a little extreme. I just throw that out there for you to consider.
What exactly is he depressed about? Is there something you can do to alleviate some of the stress he feels at work?
PS
You may want to move your thread over to Emotional Needs as this area doesn't get a lot of traffic.