Well it does sound like you are indeed striking out on a path of your own again and trying to ensure that you alone determine how you will feel, so good for you. Much better than replaying it over and over again in your head trying to figure out where you went wrong, brooding over what you did or didn't do to cause this. We're all complex creatures, sometimes doing things that have no real rational explanation.

Maybe you really didn't do anything wrong and once you bought the house and were living together he got spooked about loosing his "space". Maybe you did try too hard and he felt smothered but kept that fact bottled up inside. Not being willing to or not being able to figure out how to express true deep feelings is not an uncommon condition with men. I know I have trouble with it and it frustrates me. Maybe that's why he says there is no reason why the love withered.

There's the possibility that he truly doesn't know why, that he knows why but can't figure out a way to tell you, that he won't say because he genuinely still cares about you and feels that telling you would hurt you and he doesn't want to do that, and there's the chance that he really knows the reason but won't say because he's ashamed or trying to hide something that if you knew about would make you justifiably very angry/hurt.

This is all pretty much speculation on my part, and as they say there's always three sides to every story: his, hers, and the truth. Not that one or both are not being honest, it's just that based on the way the sexes generally see and interpret things differently, plus each person having their own individual viewpoint makes each one perceive it in their own unique way.

Maybe give him the benefit of the doubt on the return phone call. He really may have been stressed out between the personal issues and being busy at work. It seems like he at least realized that he may have not come across very well when you called him, so he called you back trying to apologize in his way. Is it possible that you were still miffed when he called back and were kind of looking for some friction? You did say you kind of told him off, which you were right to do if he indeed was being nasty. He does owe you the common courtesy of being at least civil, especially since he says you are totally not at fault.

Be good to yourself.

p.s.
Contact one of the forum moderators and ask them to change your screen name if you want to. They should be able to do it without loosing the posts you've already made.