LostAngel,
First of all, that is very brave of you for keeping up the NC for now over a month. Trust me, that is when the healing can truly begin. You are only taking steps forward whether you feel it or not...but calling him will definitely bring you a few steps back.
We all feel for you and have all been there. Something like this happened to me a few years ago, where everything seemed to be just fine and *boom* all of a sudden he wants to break up and pursue a girl he met. It was the worst betrayal and I could not get out of this black hole that I was in. An ambush like that makes you not trust even happy times. Allow yourself to hurt and be confused. Things like this can't be rationalized. What I know though is that there is NO WAY that he is not thinking of you - don't believe that b/c he is seeing someone else. I believed that too and and then my ex eventually contacted me months later and told me that he didn't stay in the next few "relationships" after me because none of them could compare to me. I don't know if this makes you feel better right now. Who knows all the reasons guys do these things, like start seeing someone right away. They deal with pain differently or they try to get over you faster. A friend of mine's ex admitted that he started dating a girl right after their breakup to help get past it. That relationship didn't last probably b/c dating someone so soon can just add to the confusion of it all.
I'm not saying that these are the things that can or will happen. I'm saying that don't kick yourself or blame yourself for anything, like thinking that it will never be reconciled if you don't contact him. It's not something that we can always control. I know what you mean though - it makes us feel incredibly alone thinking they have moved on. I honestly don't think he has 100% moved on though - I highly doubt it.
Hang in there and keep posting as you get past this!!!