Honestly man, the next thing you need to do is go find someone that you can talk to about this. It doesn't sound like your wife is that person right now; maybe she will be at some point, but right now she is not. And as much as folks here might want to help, when you come right down to it there is only so much that you can get from an online conversation.
This. This. A thousand times this.
I'm single, no kids. My closest confidants are a couple of old university friends, and my sister. My sister has her husband and kids to deal with, so I don't want to burden her too much, and there's only so much I can say to my friends (that's me, not them.)
I've been to see a shrink. It's helped - a lot. Putting things into perspective, understanding alternative viewpoints to my own; also gaining some insight to myself with an Aspergers diagnosis - it's all helped me to reach sturdier ground than I was on a couple of years ago. (There are other matters as well, to do with having to move around a fair bit to areas where I didn't have a support network, and falling into bad eating habits as a consequence, but anyway.)
The hardest step is admitting that there's a problem. You've done that. Talking about it with people, whether it be here or elsewhere, is useful. But I strongly recommend that you see your doctor, get a recommendation for a good psychiatrist, and have a few sessions. It may also be worthwhile to bring your wife along to one after you've been going for a while, to try to nut out the obvious differences in viewpoint around this (but you have to decide whether that's likely to help, or harm, the relationship; I'm of the view that openness and honesty are cornerstones of a committed relationship, but I don't know you, nor your wife. Where I'm coming from is that once you're a little more stable and solid, helping her to understand where you were emotionally may - not necessarily will; you have to judge that, not me - help get that issue out of the way so it doesn't come between you in the future. If you just shrug it off saying "it's in the past", it's far too likely to fester and come up again.)
I recently got into triathlons; that got me back onto my bike regularly (which I'm loving - it had been far too long off it), running (which I'm starting to learn to cope with, if not enjoy) and swimming (which isn't too bad, although I'm not enjoying it when I'm in a race with half metre or more swells, I must admit.) The key for me there is that there are people who implicitly expect me to be there - granted that they don't quiz me if I don't show, but it adds an extra incentive for me to stick to the schedule that simply isn't there with a gym membership.
It's easy to be an armchair quarterback, I know, but I do hope that you're getting some useful suggestions. You may have to force yourself at first, but please, do try to find something
that gives you a routine to get out of the house for a bit.
And seriously: good luck. I wish there was more I could do from here in Australia; I can only hope that what you're getting from everybody here is helping you move in the right direction.