I think he must have just realized that he 'has' me - and that I have 'demands' and 'needs' too. We don't have kids together but we were literally just planning to move to a larger house to start a family. I think that scared him off. Especially after he has made mistakes in the past in regards to his D (or at least he feels he has) and his biggest fear is to repeat those mistakes.
I always knew there was an issue there but I never thought it was so HUGE that he would just run off one day.
After 4 months I have now 'agreed' to the separation (I've just said that I was fine with it now). Not sure if that was the right move but I can't force him to work on our marriage (or on himself) if he doesn't want to. Can I?