You could have been describing me three years ago, everything is exactly the same. I was together for 17 years, we have two kids, nice house, we did break up a few years before for 6 weeks but she came back telling me she loved me and I thought we had sorted it out but obviously not.
I moved back to my parents immediately until she rented a place about 6 weeks later, it was horrible, I helped her pick it, I wanted to be friends with her and I still did things for her, worse still, she let me, she kept saying she needed space and couldnt think and I never really gave her that, I just wanted her back, I felt so weird its hard to explain, I felt like I had lost a limb or something like that, I had been with her since I was 19.
After about 6 weeks I found out she was dating and it was pretty much the hardest thing to deal with, it was horrible, I cried myself to sleep every night for months, I was constantly picturing in my head what she was doing and who she was doing it with and it drove me insane, I couldnt sleep without a tv on and started watching the same films over and over at bedtime as they somehow comforted me, I think because I by this time knew all the words, it was like having someone talk me to sleep (for the record, these were Superbad, Step Brothers, Zack and Miri make a porno and stuff like this, I could probably recite them all word for word now).
We had split in September, we had agreed to spend xmas together with the kids, it was horrible, in the end I couldnt wait for her to leave, the xmas holiday was horrible and when the bells went at new year, I spent it alone with my older daughter and cried like a baby, something that Im really ashamed off letting her see but I vowed after that I wouldnt give her another thought and would move on with my life.
It was tough for sometime after, I started dating a few months after that and met a nice girl but she wasnt my wife and we broke up, I wasnt ready and shouldnt have been dating but you do silly things to occupy your mind, it started being fun to go out and meet women though, something Id never really done before (my first girlfriend was my wife). Around March time, six months after I split up, I met a nice girl, the week after I met her my wife wanted to talk about getting back together and I thought about it for a few days and said it wasnt a good idea, it wasnt because of the new girl it was just because I new she wasnt right for me anymore and I couldnt let her do it to me a third time which inevitably would have happened.
About 6 weeks after she had spoke to me about this she had met a new guy and he moved into her house, she had been seeing him around the time that she wanted to talk about us so it was all a very quick thing and upset the kids, my eldest daughter stopped going to stay with her and now a few years on only see's her mum once a month if that which is a shame.
I dont blame my wife for leaving, Im glad that she did, Im happier now even though I dont have a house anymore and have to rent (we couldnt get it sold so i gave her it so the kids would have a home which didnt work out too well!), I still do love her and think of her as part of my family and we get on pretty well really, moreso than most couples I think, she has a new baby now who has just turned one, I dont know if that was part of the problem, she felt something was missing in her life as she turned 40.
Id say it took about 9 months to get back to normal, I started dating too soon, it is my one regret as I did hurt a girl who was lovely and it wasnt fair on her, as much as the temptation is there to fill the gap, Id leave some serious time between this especially after a long relationship, its quite easy to get dragged into something serious as you look to fill a void and its wrong, I learned the hard way and as a result I took things a lot slower with my current girlfriend to ensure that didnt happen.
Magnolia's Swingers clip is a great example, you just dont think when your going through a breakup that you will ever get over it, but you do, even the bit about missing the pain, I now look back at that point in my life and do miss it sometimes because time seemed to stop, a day felt like a month, a month a year, I threw myself into fitness and came out of it looking and feeling pretty good, and sometimes it feels like it would be nice to have the drive that I had during that period that i attempted to get her back as I had a goal and was focussed in trying to make it happen.