Most Helpful Guy
"Why does he STILL message me after all this time?"
Because he's hoping for the reaction you're having right now.
Ask yourself this: How would you feel if your BF's ex were messaging him? You wouldn't be cool with that, would you? It would feel disrespectful, wouldn't it? If I were in your situation, I wouldn't meet the ex at all. You've lived a full and happy life without him for the past five years, so why invite all that drama back into your life?
Most Helpful Girl
You say your ex was very controlling in the relationship, it seems to me that he is still very controlling. He knows/hopes how his messages will mess with your head. And he's obviously achieving exactly what he wants. Meeting up with him is a bad idea. After five years you don't need any answers for him, you just need for him to go away. You say that you aren't even mad at him for having treated you the way he has. So I am unsure what answers you are looking for. Be honest, do you have other motives for wanting to meet up with him? Does it flatter you that he sends you these messages saying he's still got feelings for you?
I think that you should simply block this guy and concentrate on your current relationship.