An unusual exboyfriend question. ?

My exboyfriend and I ended on very bad terms in may after 1 year and 8 months. (I broke up because he treated me like garbage). I have a new amazing boyfriend and my ex has a new girlfriend who i used to be friends with. He has always been naturally very quiet (kind of comes off as unfriendly) and hardly ever expresses emotion. We still work together but we never talk or make eye contact. Just recently I've started to approach him at work with a very enthusiastic "Hey How are you?" He says "good". I find its kind of a fun game to play to see if I'll ever get more out of him than a "good". He always seems so sad and depressed. I just wonder what he is thinking? Doesn't he want to show that he's happier off without me?