Why can't he just talk to me?

I understand that you are a very caring person and would like to be able to talk to your ex like a normal person. But, I feel for him. He was in love with you. It may take him longer than this to get back to himself - in fact, seeing you is probably very difficult for him. Please understand that all of us are so different and getting over someone is far from easy. He will, in time, be able to socialize but right now he just can't. He tries but as you can see, he backs off because it is still painful for him. Give him more time to adjust to what is and start to move forward. I live in a small town so I do understand this situation very well.