Sounds like he is dating someone new. Most guys won't admit it and they try to just avoid confrontation. I had an ex that would talk to me and we would be friends but once he met another girl, he would fall of the planet.
It's good that you can be cordial to your ex, but best friends is next to impossible because where there was once love, there can be some hurt feelings. Sorry you have to go through that! It was painful for me at first but now I actually joke with my ex about it, even though he STILL does it!!!
I'm not good at beating around the bush or sugar-coating things. My responses are never personal vendetta's on your emotional state. It is what it is, whether you choose to accept it or not. <3