Most Helpful Girl
Chances are, he's not completely over her. Being married to someone is a big deal, obviously he loved her and they were together for a very long time. Those feelings don't just disappear overnight.
I do think you should talk to him though because while it's understandable that he would still have feelings for her, that's not fair to you. If he can't commit himself to you 100% then it's not fair for him to be with you while still having feelings for his ex. You should ask him about it and have a mature conversation to see where he's at right now and how he feels.