The relationship between you and your ex boy/girlfriend is always awkward. Period.
I do not care if you are the nicest person in the whole world or your ex is the nicest person in the whole world or you guys had a decent break-up or you guys still maintain some kind of friendship over the years – the relationship between you and your ex is bound for awkwardness. Everyone who says otherwise, I am very sorry, I would never ever agree with you.