I'm in a similar situation.
I'm 50, been married for 20 years and been with the same woman for 24 years - nearly half my life. I loved her dearly and still do.
For the last two and a half years I'd been a bit depressed, but not about our marriage.
In April my wife told me, completely out of the blue, that she wanted a divorce. It hit me like a truck.
Roll it back to January. I was a bit depressed, we argued (about once every 6 weeks, and mainly because I was having a strop). But on January 6, I realised I had to turn myself around, so the first thing I did was quit smoking, and started to appreciate what I had, not focus on what I didn't have. I wanted for nothing and felt secure and happy in my marriage.
At the end of January I got in a temper, lost control of my mouth and called her some names. I was bang out of order and didn't mean any of it. I felt that I was the only one who cared about getting things done in the house - 'sweating the small stuff', my wife called it.
A few things had got on top of me - not smoking of course, feeling down in my job (I work with some soulless, two-dimensional people with whom I have little to no affinity, and my job causes me constant frustration, which stays with me when I return home), sorting out paperwork after my mother's death the previous year, a case of optic neuritis (more of that in a bit) and a wayward flouncy 12-year-old daughter who wouldn't do her chores and made my life difficult. I understand now that she was just being herself. We haven't fallen out.
But after me blowing my mouth off things returned to what I thought was normal. We chatted, spent evenings together watching movies, we were loving towards each other and nothing seemed to have changed.
Back to the optic neuritis thing. Long story short, it turned out to be an early symptom of multiple sclerosis. I got the preliminary diagnosis in March, but I didn't care. I had a happy marriage and a wife I loved. My first reaction was that at least I wasn't being told she had it, or any of my kids. I'd deal with it.
April came around, we took a week off to spend time with the kids during the holiday and I just decided I would become more happy, which I was.
So the end of the week comes along. We'd both been to London for a day out, been out with the kids, spent some happy days together.
At the end of the week she was sitting in the garden looking a bit glum. I asked her what was up, and she told me she didn't love me any more and wanted a divorce. I was destroyed. She said that when I called her those names in January, the love just "switched off".
A day later and I find that she's been messaging some low-life she went to school with on Facebook just the night before. "Flirty texts" she called them. "At least there's a man paying me some attention" she said.
I lost my sh*t and did some things I'd never have considered in my life before. I bugged her car and the house, and she caught me. From that point on she completely closed off to me, changed all her passwords and hid her phone when anyone walked past.
However, she said she wasn't messaging him any more.
She became a stranger to me. She acted swiftly. Our accounts were separated, she went to see a solicitor and started divorce proceedings, which are now on the way to a decree nisi.
I now live alone in a small rented house nearby (so I can help with the kids) though I am not allowed to go to the marital home any more.
I was still suspicious. One day I left work and drove past our house to see the car of the guy she'd been messaging on Facebook parked outside. She'd been lying to me.
She forced me to move out, but said that we should avoid any acrimony for the sake of the kids, which she has stuck to.
So here I am now. Sitting alone, bereft, bewildered. Utterly broken inside. Torn from a marriage I was happy in, and a house into which I poured my heart and soul for 18 years.
Despite me being a bit down, I never looked at another woman. I was dependable, hardworking, attentive and, though I say so myself, a great dad. My kids would say the same, I think. They are all down about it, and it's been mentioned in their school reports.
I didn't want to go out as much as she did because I wanted to stay home and make sure the kids (7, 12 and 15) were OK. Plus I was tired, possibly because of the MS. She said that the oldest would be fine babysitting the other two. He sits attached to his XBox all night with the door closed. He's not a good babysitter.
She's all happy-happy about everything. "It'll be fine" she says. "You'll find someone else", "MS is just one of those things you have to manage", and so on. She has shown an inhuman lack of empathy.
And then I read that MS can cause you to have uncontrollable mood swings. But that has no weight with her, and she says I'm trying to find an excuse (which I am not). I have always believed in taking the full force of the consequences of my actions square on the chin. But it most certainly had something to do with me losing control of my mouth back in January. It's all academic anyway, because she doesn't love me. And that's her get-out argument for everything now.
If it wasn't for the kids they'd have cut me down from a tree weeks ago. People tell me that it's a tough time, and I'll move on eventually, and I'm sure they're right. But right now I'm in nightmare limbo.