Why won't he answer me?

Maybe his girlfriend wants to ensure that the two of you are still talking. If you all keep the lines of conversation open, no one will be in the dark about each other's feelings, and there will be less desire or incentive to cheat.

Or, he might just want an excuse to show off his new girlfriend--proof that he has moved on.

I wish I knew I'm in the same boat. I think he still cares for you can so he wants to talk to you on his time only. If you text him it makes him feel good and thinks that you still care for him and well since that's all he cares about he won't talk back. that's just what I think I don't know for sure. My ex broke up with me and then dated someone else within a month and called me emailed me for 3 months. anyway I know how you can be confused about this but the best way is to not talk to him its to soon tell some time go by. try to find yourself during this time try to find what makes you happy and only you. I know this may seem selfish but now its time to only think about you.