1. I think you should talk to A again. Even if they don’t want to talk anymore, you need closure in order to move on. So try to gather the courage to talk again, don’t expect anything, and just see what happens.
2. It’s possible your feelings are returning for this other guy. It’s normal to enjoy talking to him, but if you don’t want anything to interfere with your current relationship, then you might want to consider at least not talking to him as much as you are now.