Well, first I'd like to say that you're lucky your wife is at least 'supportive'. It took four years to convince my husband that my depression/bipolar disorder was even real. You say your wife doesn't understand, and unless she has been through this kind of thing, there is no way that she can. I've spent 12 years now trying to make my husband understand what it's like to be me, and I still don't think much of it has sunk in. But, supportive is a great first step.
You're obviously having some kind of problem, and since you came here and posted it for all to see, you obviously want to do something about it, which is great. You do have to understand that you are the only one who can. There is plenty of help out there, loads of support, but you have to go and ask for it. You need to see a doctor, talk about medication, about therapy, about all the various avenues of help and support that are available, and there are plenty.
So tell your wife that you think you might have depression, tell her you want to see a doctor about it. Ask her to come with you if you need moral support - don't freeze her out of it. When you see the doctor, make sure you tell him/her everything. Make a big old list of the things you've been thinking and feeling since this whole thing started. Every little thing, no matter how insignificant you might think it is. The more information they have, the better equipped they'll be to help you.
Don't be embarrassed, don't hold back. You are a human being, you are entitled to respect and you are entitled to be happy and healthy, and it takes guts to go out there and get that for yourself. It took guts for you to even write your post. A hell of a lot of people don't even get that far. So, you've taken this first step, go and take your next one. Resolve to make a phone call to your doctor as soon as the clinic is next open. If they have trouble fitting you in, tell them that it's urgent, that you're having mental health issues that you need help with now, that you're in danger of losing your job because of it. Say whatever you have to say to get in and see someone as soon as possible, and then don't leave that doctor's office until you're satisfied that you've been understood, that this doctor is putting things in motion. If they just offer you pills and nothing further, ask for something further. Tell them you really want to kick this thing's arse, you want to hit it from every possible angle, and if they can't help you, ask for referrals to people who can.
Stand up for yourself, let your wife help you as much as she's able, and know that things absolutely can get better.
