I am a guy. Actions speak louder than words, and him saying that he still wants to be with you while his actions indicate the opposite is a red flag. Him moving out is not a good sign, especially if you had intentions of marriage. You didn't explain a lot in your post, but I can't think of a reason why he would move out other than he is beginning a process of breaking up with you.
It doesn't matter who's fault it is - the bottom line is you both know each other very well and he took a step towards moving away from you - he's moving on. At this point you need to force communication and force the issues to be addressed. Force a mutually content reconciliation or break up with him. The worst thing you can do is waste time in a dead end relationship. Some guys can't commit but they want to keep the girl around - probably not in your best interest.
And don't let the four years you spent together make you feel that you have too much invested in him to move on yourself. You might want to at least stop seeing him and spend time apart to get perspective. Break ups hurt, but what hurts more is time lost dragging out a dead end relationship, and not being with the one you should be with.